To access the menu bar of X-plane, you need to reach the top of your screen with your mouse pointer, when the sim is running. (Not in the home screen)
You will find flight, views, etc... and plugins
It is rarely necessary to reinstall the whole sim but it's rather easy to do. You just need to remember your product key, which is asked regularly anyway.
X-plane interferes neither with system files nor with registry. Everything is inside the X-plane folder. Settings, screenshots, plugins and other additional products.
So it is easy to move, copy, backup, uninstall or install. The only constraint is :
1 licence = 1 instance running at a time
Moreover, it is very important to place X-plane somewhere you have no permission restrictions, in terms of file access.
You can find X-plane manual either in X-plane folder (I don't remember where precisely), or here :