I don't rememeber how, but you can put any game or program into steam. it's not hard but i need to google it.

Last time i used a disc, 20 years ago. the game(skyrim) needed Steam to play the game. As soon i ran the disc it asked me to download Steam. Anyway, if not! you have to bookmark your game into your library.

Okay Steam app -> 'games' tab on top of screen -> select 'Add a non-steam game to my library'

if its a steam game, you will need to add the game key to steam
steam -> game -> activate a product
and enter the game key

you can use the disk to install the game with steam to save some download, but steam will also download and apply patches from the internet

Thanks for the help guys