Follow these steps to add sub-users to your control panel account.
Step 1: Login to the game control panel.

Step 2: Click on your name in the control panel.

Step 3: Click on the sub-users icon.

Step 4: You will see your name and a blanked out password in the fields.

Step 5: Replace them with a username and password for your sub-user.

Step 6: Click the Game/Voice Service Permissions tab.

Step 7: Be sure to give them access to this service permission, otherwise, they won't be able to control that server.

Step 8: It's unchecked if you have multiple servers and only want them to control one.

Step 9: Set their other permissions (Letting them start/stop the server may be another good option.).

Step 10: Click Save when you're finished.

Step 11: Give them their login information.