Help with installation please

I've bought a couple of brand new FM games with codes, after failing with a couple of 2nd hand ones that had used the steam codes

Reseaching around, i find you can install them and add them to steam, or you can just install it from the disk and steam checks the code.

Can someone clarify please, i don't want to make a mistake and invalidate the code. Whats the best way to do it

And is it right you can retire for 20 years to generate fuctional players ? Whats the best way to do this ?

I have installed FM2009, which won't accept the key as it says it is temporary, even though I installed the game outside of STEAM

I also installed FM2010 and it didn't ask for a key, but is blocking me (see above link) all the way until it says "Actions". (see link, although my windows 11 screen is different and doesn't ask for Actions)

I have rebooted the PC with ransomware turned off, but still the PC won't save games. It works perfectly otherwise.

https://www.dpscomputing.com/blog/2022/04/15/football-manager-2022-the-game-could-not-be-saved/