To disable a user, access the "Team" section, and click the "Disable" icon on the far right of the user. This will not delete the user data and you will still be able to bring them back to your team. However, the disabled team member will not be able to access your workspace. View these archived users by clicking the "Show Inactive" filter.
To delete a user, first make sure that the user is disabled. Access the disabled member through the "Show Inactive" filter. Then, click the "Delete" icon on the far right of the user. This will permanently delete all member data. This action cannot be undone.