I'm a current member of stadia and got 2 months free and just got the stadia kit from Google with free months free but have no idea how to add that on to my account I can't see no option?????
as far as I know, those are not combineable. That means you have 2 or 3 month.
I have confirmed with Stadia support that the 3 months free is ONLY for new accounts. If you already claimed the 2 free months you can't also claim the 3 months that come with the bundle. It has to be applied to a new account.