Beamer Installation

Question

I am new to Latex especially with beamer... Now I have been trying to compile a file as shown but I got the error of Latex error: Beamerthemesharelatex.sty not found .. I had read instruction about downloading the beamer package and I downloaded it, but I do not understand the read me file at all, which files shall I copy and where to paste .. Please help

\documentclass{beamer}
  \usepackage[english]{babel}
  \usepackage[utf8]{inputenc}
  \usepackage{times}
  \usepackage{amsmath,amsthm, amssymb, latexsym}
  \boldmath

  \usetheme{Sharelatex}
  \usepackage[orientation=portrait,size=a0,scale=1.4]{beamerposter}


  \title[Beamer Poster]{ShareLaTeX example of the beamerposter class}
  \author[sharelatexteam@sharelate.com]{ShareLaTeX Team}
  \institute[Sharelatex University]
  {The ShareLaTeX institute, Learn faculty}
  \date{\today}
  \logo{\includegraphics[height=7.5cm]{SharelatexLogo}}

  \begin{document}
  \begin{frame}{} 
    \vfill
    \begin{block}{\large Fontsizes}
      \centering
      {\tiny tiny}\par
      {\scriptsize scriptsize}\par
      {\footnotesize footnotesize}\par
      {\normalsize normalsize}\par
      ...
    \end{block}

    \end{block}
    \vfill
    \begin{columns}[t]
      \begin{column}{.30\linewidth}
        \begin{block}{Introduction}
          \begin{itemize}
          \item some items
          \item some items
          ...
          \end{itemize}
        \end{block}
      \end{column}
      \begin{column}{.48\linewidth}
        \begin{block}{Introduction}
          \begin{itemize}
          \item some items and $\alpha=\gamma, \sum_{i}$
          ...
          \end{itemize}
          $$\alpha=\gamma, \sum_{i}$$
        \end{block}
        ...

      \end{column}
    \end{columns}
  \end{frame}
\end{document} 

Answer 1

The error message says beamerthemesharelatex.sty is missing, not beamer itself. That file defines a theme, that in the template you use is chosen with \usetheme{sharelatex}.

(Note that this is case sensitive: if you have \usetheme{sharelatex} it looks for a file called beamerthemesharelatex.sty, while if you have \usetheme{Sharelatex} the file should be called beamerthemeSharelatex.sty.)

If you comment out/remove \usetheme{sharelatex} it will likely work, assuming beamerposter is installed (which it might well be). If you want to use that theme, then download the mentioned file from ShareLaTeX, it is for example a part of this template: https://www.sharelatex.com/templates/presentations/beamerposter---flow-multicolumn Place it in the same folder as your .tex file to make it available.

Regarding the code in your question, it has one \end{block} too many, which causes an error. Note at the start of the frame environment you have this:

\begin{block}{\large Fontsizes}
  \centering
  {\tiny tiny}\par
  {\scriptsize scriptsize}\par
  {\footnotesize footnotesize}\par
  {\normalsize normalsize}\par
  ...
\end{block}

\end{block} % <-- delete this

Remove the second \end{block}.