Ableton Link is a system for synchronizing multiple music applications, which may be running on different devices, by providing unified, real-time tempo control. Link-enabled programs find each other automatically when they are on the same network. Any "player" in the network can change the tempo and the others follow.
To enable Gig Performer to sync to Ableton Link, click on the Link button in the upper toolbar (A) or enable the toggle button in the drop-down menu window (B):
No configuration of any kind is necessary, just turn it on.
Visit this blog article to learn how to synchronize Gig Performer's tempo to an external MIDI clock or Link-enabled products.