Hi @Kim Angeles ,
To leave a board in Trello, open the board menu on the right side of the board, click "More" and choose "Leave Board". This will remove your account from the board, which means you may no longer be able to access it.
For more information, please read this : https://help.trello.com/article/804-leaving-a-board-in-trello
Thanks ! Hope this solves your problem.