Here is how you find a team that you've joined already on GoJoe:-
Open the GoJoe app > press challenges
Press into the challenge you are in > press the teams tab > press the filter button (which is to the right of the word leaderboard) > search for your team name > press enter (if you are unable to remember your team name, press the solo tab > search for your personal name > your team name will be displayed under your personal name).
Once the challenge starts, your team and solo position will be pinned to the leaderboard so you will not need to do the above searching.