If you want to remove access for a user you can delete the corresponding account. Please note that this will also delete all systems and patch alerts created by this user, including shared ones.
To delete a user follow these steps:
Step 1: Open user management
Step 2: Delete the user
On the right side you can see all currently active users on your account. To delete a user click on the “Delete” button next to the user email address:
Confirm the deletion in the next step. After this the user and all associated data is deleted.