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.

We're going to start off with the Addons tab, you should know it well, it looks like this:

First off, we're going to click in the right pane, and select Add Group

Next we're going to create a name for this group that identifies the mod, I personally use + DLC - Global Mobilization. (The plus keeps it sorted at the top.) Select Ok when you're content with your choice.

Next we're going to wander over to the DLC tab, here's a picture of where it's hiding:

Once there you're going to want to drag the GM “mod” from the left pane, in the the DLC folder we made on the right pane.

Click the little plus button to make sure you added it correctly, it should look like the below image.

Last but not least, check the box to enable the DLC.