As an administrator / power user of the account, you have the ability to grant access to or remove users from your Order Manager Dashboard.
From your Order Manager Dashboard, select People at the top of the screen.
After entering the People screen, you will see a blue Invite User button near the top right. Here you can enter an email address for the user to invite them to your Order Manager. You can also choose to allow this user to have Admin privileges by selecting the checkbox at the bottom of the screen.
Removing Users from Order Manager
When viewing the list of active users on the People screen, you can remove a user by clicking the trash icon located to the right of their name.