GCA can update a lot of the files it uses through the Package Manager in the Check for Updates system. It can even tell you that a new update for itself is available. Unfortunately, GCA can not update its primary program files through this system. To update GCA itself, you have to reinstall it from the setup program available on Warehouse23–the same way you originally installed GCA.
Here’s how you do that.
In the future, SJGames will no longer be updating the GCA available at the OLD store, but for the time being they have graciously updated that download to the current version. If you originally purchased GCA through the NEW store, however, you must download the updated GCA installer from there.