I wan't to play post stroke but can't use my mouse right now!

jman81647  Steam will install a new game into whatever you've designated as the Steam library.  You can move it after the fact if necessary, or create a new library beforehand.

https://help.steampowered.com/en/faqs/view/4BD4-4528-6B2E-8327

It sounds like you wouldn't need to change anything, but if you wanted to, it should be simple enough.