If you have access to the loads for multiple airlines, you can add up to three additional airlines for which you'll see open load requests.
To do so, open the StaffTraveler app or point your browser to StaffTraveler for web.
Tap or click your profile picture in the app's top-right corner and choose Profile & settings. Scroll down to the section Additional airlines. Here, you can add the extra airlines for which you can provide loads.