Clear Backblast's usage of Global Mobilization consists of 2 parts.

1. A repository of compatibility data
2. How to load GM with the modset

This guide will guide you along setting everything up.

The compatibility repository autoconfig is located at http://cdn.clearbackblast.com/gm/.a3s/autoconfig

To add the repo to Arma3Sync, follow the setup guide starting at step 5, here.