Follow these steps to add sub-users to your control panel account.
Step 1: Login to the game server Control Panel
Step 2: Click on Sub-Users in the control panel's left menu.
Step 3: Replace them with a username and password for your sub user.
Step 4: Click the Game/Voice Service Permissions tab.
Step 5: Be sure to give them Access to this service permission, otherwise, they won't be able to control that server.
Step 6: It's unchecked in the event that you have multiple servers and only want them to control one.
Step 7: Set their other permissions (Letting them start/stop the server may be another good option.).
Step 8: Save.