Your choice of editor does not affect the packages you can install. You can update your TeX distribution, install additional packages, classes and fonts, and create your own independent of your editor. Your editor does not, that is, stop you using pgfornaments and I'm assuming nothing else does, so if you like its decorations, you should certainly install and use it.
decorule offers a decorative, swelled rule which does not depend on the installation of additional ornaments or fonts. Instead, it creates the rule from a character included in all TeX distributions. However, the results are predictably somewhat less satisfying than a proper typographic decoration might be.
\documentclass{report}
\makeatletter
\def\@makechapterhead#1{%
\vspace*{-5em}% Space above number
{\parindent \z@ \normalfont
\interlinepenalty\@M
\LARGE\centering \textbf{\itshape\thechapter}%
\decorule
\par\vspace{0.5em}% Space between number and title
{\LARGE\itshape#1}%
\par\vspace{4em}% Space between title and text
}}
\makeatother
\usepackage{decorule}
\begin{document}
\chapter{Chapter title}
\end{document}
Or you could try swrule. Again, no special stuff needs to be installed. However, I've never managed to produce satisfactory results:
\documentclass{report}
\makeatletter
\def\@makechapterhead#1{%
\vspace*{-5em}% Space above number
{\parindent \z@ \normalfont
\interlinepenalty\@M
\LARGE\centering \textbf{\itshape\thechapter}%
\par\vspace{0.25em}% Space between number and title
\mbox{}\swrulex{.3\textwidth}{.25pt}{3.5pt}
\par\vspace{0.25em}% Space between number and title
{\LARGE\itshape#1}%
\par\vspace{4em}% Space between title and text
}}
\makeatother
\usepackage{swrule}
\begin{document}
\chapter{Chapter title}
\end{document}
If you don't mind the overhead, you could always draw one:
\documentclass{report}
\usepackage{tikz}
\newsavebox{\myrule}
\sbox{\myrule}{\tikz {\path [fill, draw] (0,0) [out=0, in=180] to +(.125\textwidth,1pt) [out=0, in=180] to +(.125\textwidth,-1pt) [out=180, in=0] to +(-.125\textwidth,-1pt) [out=180, in=0] to cycle;}}
\makeatletter
\def\@makechapterhead#1{%
\vspace*{-5em}% Space above number
{\parindent \z@ \normalfont
\interlinepenalty\@M
\LARGE\centering \textbf{\itshape\thechapter}%
\par\vspace{0.25em}% Space between number and title
\usebox{\myrule}%
\par\vspace{0.25em}% Space between number and title
{\LARGE\itshape#1}%
\par\vspace{4em}% Space between title and text
}}
\makeatother
\begin{document}
\chapter{Chapter title}
\end{document}
The advantage of creating \myrule as a box is that the TikZ picture only has to be rendered once for the document, regardless of how many times it is used. If, however, you want to be able to alter the length of the rule within the document, a command will work better:
\documentclass{report}
\usepackage{tikz}
\newcommand*\myrule[1][.25\textwidth]{%
\tikz {\path [fill, draw] (0,0) [out=0, in=180] to +(.5*#1,1pt) [out=0, in=180] to +(.5*#1,-1pt) [out=180, in=0] to +(-.5*#1,-1pt) [out=180, in=0] to cycle;}}
\makeatletter
\def\@makechapterhead#1{%
\vspace*{-5em}% Space above number
{\parindent \z@ \normalfont
\interlinepenalty\@M
\LARGE\centering \textbf{\itshape\thechapter}%
\par\vspace{0.25em}% Space between number and title
\myrule%
\par\vspace{0.25em}% Space between number and title
{\LARGE\itshape#1}%
\par\vspace{4em}% Space between title and text
}}
\makeatother
\begin{document}
\chapter{Chapter title}
\end{document}
Here, \myrule is .25\textwidth by default but \myrule[some length] will override that default. For example, \myrule[.1\textwidth] would produce
This can then be adapted to permit changing the length as appropriate in the document:
\documentclass{report}
\usepackage{tikz}
\newcommand*\myrule[1][.25\textwidth]{%
\tikz {\path [fill, draw] (0,0) [out=0, in=180] to +(.5*#1,1pt) [out=0, in=180] to +(.5*#1,-1pt) [out=180, in=0] to +(-.5*#1,-1pt) [out=180, in=0] to cycle;}}
\newlength\myrulelength
\setlength{\myrulelength}{.1\textwidth}
\makeatletter
\def\@makechapterhead#1{%
\vspace*{-5em}% Space above number
{\parindent \z@ \normalfont
\interlinepenalty\@M
\LARGE\centering \textbf{\itshape\thechapter}%
\par\vspace{0.25em}% Space between number and title
\myrule[\myrulelength]%
\par\vspace{0.25em}% Space between number and title
{\LARGE\itshape#1}%
\par\vspace{4em}% Space between title and text
}}
\makeatother
\begin{document}
\let\clearpage\relax% only for testing!
\chapter{Chapter title}
\setlength\myrulelength{.2\textwidth}
\chapter{Another chapter title}
\end{document}
To have the length automatically adapt depending on the length of the chapter title, you might try this:
\documentclass{report}
\usepackage{tikz}
\newcommand*\myrule[1][.25\textwidth]{%
\tikz {\path [fill, draw] (0,0) [out=0, in=180] to +(.5*#1,1pt) [out=0, in=180] to +(.5*#1,-1pt) [out=180, in=0] to +(-.5*#1,-1pt) [out=180, in=0] to cycle;}}
\newlength\myrulelength
\setlength{\myrulelength}{.1\textwidth}
\makeatletter
\def\@makechapterhead#1{%
\vspace*{-5em}% Space above number
{\parindent \z@ \normalfont
\interlinepenalty\@M
\LARGE\centering \textbf{\itshape\thechapter}%
\settowidth{\myrulelength}{\LARGE\itshape#1}%
\par\vspace{0.25em}% Space between number and title
\myrule[.8\myrulelength]%
\par\vspace{0.25em}% Space between number and title
{\LARGE\itshape#1}%
\par\vspace{4em}% Space between title and text
}}
\makeatother
\begin{document}
\let\clearpage\relax% only for testing!
\chapter{Chapter title}
\chapter{Another chapter title}
\end{document}
pgfornamentsor whatever has what you want, just install it. Latexian doesn't have anything to do with it: it is just executing binaries from the TeX distribution under the hood. Those will be able to use whatever packages you have installed, including ones not in TeX Live and including any you write yourself. – cfr May 01 '15 at 22:47