Q: How do I remove a user from my project?
A: With the project selected and in context, click on Project Settings 
and select the Project Team tab.
Remove from Project
Click the checkbox to the corresponding user(s) you wish to remove and click the Remove from Project button:
Note: The user you wish to remove cannot be the only assignee on any tasks. If they are currently the only person assigned to a given task, you must reassign that task to a different person first. Once all conflicts have been resolved, you should then be able to remove the user without issue. To learn more about this click here.