TUTORIAL 1
With one change at login, Steam stops asking for a verification code every time you open the game.
Open the Steam client on your computer
If you are already signed in, sign out before continuing.
Type the username and password the store sent
Check it letter by letter. Steam locks you out for a few minutes after several wrong attempts.
Check "Remember me" before signing in
This is the step that makes the difference. With it checked, Steam saves this computer as trusted and stops asking for a code on every login.
Redeem the verification code on the store page
On the screen asking for the 5 character code, open the site, paste your single use code and copy the Steam Guard code.
That is it, go play
Next time Steam signs you in directly, with no code.
Do not change the password and do not turn on the authenticator on this account. Both break the access immediately and the game stops opening.