Yes you install it through the software centre thingy. You don't have it twice because what you have is two different version of the software in two different systems. Basically what you're doing is splitting your computer into two computers. Think of Windows and Linux as two computers that just happen to be sharing the same hardware. A bit like a flat share. They're never home at the same time. But Linux is the creepy one that can rummage through Windows' stuff. Windows doesn't even know Linux exists in the flat and can't see its stuff.
Linux sniffs Windows' undies while it's out at the shops![]()