The very first sentence of the MnSymbol manual reads:
MnSymbol is a font of mathematical symbols designed as companion to Adobe MinionPro, but it might also fit well to other renaissance or baroque faces.
In other words, MnSymbol doesn't change the default math font, it merely provides a set of matching mathematical symbols. If you want to use Minion Pro for letters and numbers, you must install Minion Pro on your system.
There are several options for doing so, depending on your LaTeX-engine. (You need to have access to the OpenType fonts in each case.)
You can use Minion Pro with pdflatex, XeLaTeX and LuaLaTeX but MnSymbol does not play nice with the last one.
pdflatex
This one is the most complicated. There are several good scripts and tutorials around. This one is for MiKTeX 2.9: Installing Minion Pro on Windows
Here is a tutorial, which explains, how to install Minion Pro for MiKTeX 2.9: http://kobi.nat.uni-magdeburg.de/patrick/pmwiki.php?n=Wiki.HOWTO-InstallMinionProInLATEXOnWindows
If you succeeded use:
\usepackage[mathlf,footnotefigures]{MinionPro}
\usepackage{MnSymbol}
XeLaTeX
Install the OpenType font on your system and put something like this in the preamble of your document:
\usepackage[MnSymbol,quiet]{mathspec}
\setmathsfont(Digits,Latin,Greek)[Numbers={Lining,Proportional}]{Minion Pro}
\setmathrm{Minion Pro}
\setmainfont[Ligatures = {Common,TeX},
Numbers = {Lowercase, Proportional},
SmallCapsFeatures = {Letters = SmallCaps,
Numbers = Lowercase,
Kerning = Uppercase,
LetterSpace = 5}]{Minion Pro}
mnsymbolonly. The question you've linked is about Minion Pro. I know I need the fonts forminionpro, but are those files required also formnsymbol? – Arch Stanton Dec 06 '14 at 10:15$123$ $Oh$ $come$ $on$ $be$ $Minion!$. The symbolsMnSymbolprovides is listed in the documentation. – DG' Dec 06 '14 at 15:04$...$was provided by a math typeface (as for Euler). – Arch Stanton Dec 06 '14 at 18:34