To make them right aligned you need to modify the super glossary style. This is simple to do, but you need to look up the definition of the original style.
From glossary-super.sty:
\newglossarystyle{super}{%
\renewenvironment{theglossary}%
{\tablehead{}\tabletail{}%
\begin{supertabular}{lp{\glsdescwidth}}}%
{\end{supertabular}}%
\renewcommand*{\glossaryheader}{}%
\renewcommand*{\glsgroupheading}[1]{}%
\renewcommand{\glossentry}[2]{%
\glsentryitem{##1}\glstarget{##1}{\glossentryname{##1}} &
\glossentrydesc{##1}\glspostdescription\space ##2\tabularnewline
}%
\renewcommand{\subglossentry}[3]{%
&
\glssubentryitem{##2}%
\glstarget{##2}{\strut}\glosentrydesc{##2}\glspostdescription\space
##3\tabularnewline
}%
\renewcommand*{\glsgroupskip}{%
\ifglsnogroupskip\else & \tabularnewline\fi}%
}
Since it is a super tabular environment you only need to change the \begin{supertabular}{lp{\glsdescwidth}}
to \begin{supertabular}{rp{\glsdescwidth}}
. To setup your own style based on an existing style example 20 in Sec. 15.2 from the glossaries user manual is helpful. For your case this is adding the following to your preamble:
\newglossarystyle{mysuper}{%
\setglossarystyle{super}% base style on the list style
\renewenvironment{theglossary}%
{\tablehead{}\tabletail{}%
\begin{supertabular}{rp{\glsdescwidth}}}%
{\end{supertabular}}%
}
and to change \setglossarystyle{super}
to \setglossarystyle{mysuper}
.
The full change to your MWE would be this:
\documentclass{article}
\usepackage{glossaries}
\makeglossaries
\newglossarystyle{mysuper}{%
\setglossarystyle{super}% base style on the list style
\renewenvironment{theglossary}%
{\tablehead{}\tabletail{}%
\begin{supertabular}{rp{\glsdescwidth}}}%
{\end{supertabular}}%
}
\setglossarystyle{mysuper}
\newglossaryentry{Example}{name=Example, description=an example}
\newglossaryentry{EX}{name=EX, description=another example}
\begin{document}
I use \gls{Example} and \gls{EX} in my text.
\printglossaries
\end{document}
resulting in:

Note: I also changed where you define your entries to after \makeglossaries
. In your case it didn't seem to matter, but is the recommended method in the manual.