Go to your account settings by choosing 'Settings'.
Click on the 'Users & Permissions' tab.
Click on the 'Add User' button.
Define the user by adding the following mandatory information: email address, name, roles.
Click on 'Confirm' button to finish setting up the user.
If there is a need of editing a certain user or to disable a user:
Select the specific user on the users list of the account.
At the bottom, choose 'Edit user' if you need to modify it or 'Disable user' if you would like to revoke a user's rights to your account.