If a club admin or team admin adds you by email, you'll get an invite to join their club on Dugout.
If you're brand new to Dugout: the invite link takes you through normal sign-up first, including your name, email, and agreement to Dugout's own Terms of Service and Privacy Policy. Only once your account exists do we show you the actual invite: the club's name, crest, and the role you're being offered, with clear Accept and Decline buttons. These are deliberately two separate steps. Agreeing to use Dugout at all is different from agreeing to join a specific club, which shares your name, stats and photo with that club.
If you already have a Dugout account: log in using the email address the invite was sent to. Any pending invite will show up straight away as a banner, and in a persistent list in your account settings if you don't act on it immediately.
Accepting adds the club to your account alongside any others you already belong to. It never changes or removes your existing club memberships. Declining just marks the invite as declined; your Dugout account itself is unaffected either way.
One thing to watch for: if you're logged in as one email and you click an invite sent to a different one, you'll need to log out and sign in as the invited address first. An active session won't silently absorb someone else's invite.