If you have been invited to your club using the same email address, just go to your desktop computer and go to: www.clubster.com click on "Sign up" in the top right corner...enter your email...and then you will be asked to Log in again to confirm. Once logged in...both clubs will automatically be linked.
You can then go into Settings > Club Memberships and select which club is your Home Club.
The Home Club is the club name that will appear at the top of the Clubster app. You will be able to toggle between the multiple clubs on both mobile and the desktop app.