Removing a user is very easy. Firstly you must be the Admin of the team to do this.
There are 2 ways to remove a user:
Remove a user from a Sprint Retrospective.
This means that the user won't contribute with feedback for that Sprint Retrospective. Go to Your Retrospectives page, select a retrospective, and remove a user from the Attendees section by clicking on the bin icon.
2. Remove a user from your team.
In order to remove a user, you must navigate to the Members page, click vertically aligned dots on the Team Members section. Look for the users you want to delete from the team and click on the Remove from the menu.
Once you do this you will see a dialogue to confirm and depending on the role of the user, they will no longer have access to the data or stop receiving forms and communications for that team.