To join tournaments, go to Play vs. Kid and click on the tournament you want to join to the right hand side of the screen (you can join a ChessKid tournament 15 minutes before start time--join early so you don't miss the first round!). The tournaments have various time controls and numbers of rounds, so be sure you can commit to playing for the duration before you join. When your round is over, you can watch other games still in progress. The next round will be paired when everyone has finished playing the current round, so stay online. Good luck!
Chess.com Tournaments: Join tournaments in Live Chess. Click on Tournaments to see which ones you are able to join. You can join a Chess.com tournament an hour before start time.
Parents should consider enabling SAFE MODE for any child's accounts who just wants to play chess and disable messages, chats, and comments (you can limit messages to friends in the settings). Read how to enable SAFE MODE here.
RATED tournaments on Chess.com : The USCF allows rated rapid and blitz tournaments to be conducted on Chess.com . The results will affect your Online Blitz or Online Rapid rating only. To play a USCF rated tournament online, you have to authenticate your US Chess membership by completing a Google docs form that Chess.com created. You can find the form here.
In the meantime, join the ChessKid Official Club and play numerous tournament games with kids across the country! When you first log in, scroll down on the left menu until you see Connections. Click on that and then Clubs. To the right you will see your clubs and Public Kids Clubs that you can join.