Hi wrightylplp,
Your code cannot install another app. Windows Store Apps are installation is done only by the Store. Your app does not need and cannot have any installation code.
You may want to watch this video that explain the Windows runtime internals and have some information on how Windows Store Apps are installed:
Windows Runtime internalshttp://channel9.msdn.com/Events/BUILD/BUILD2011/PLAT-875T
Cheers
Celso