GGPoker offers PokerCraft, their own poker analysis website, which allows you to download your hands within 90 days after you've played them.
To download the hands, log in to GGPoker client and click on the PokerCraft link located in the toolbar at the bottom of the client.
This will open the my.pokercraft.com website.
On the left-hand side there is a menu where you can select different types of games available, i.e. Hold'em, PLO, My Tournaments, Spin & Gold... Select the desired format, check the boxes for the sessions or tournaments you want, and click the Download button on the right-hand side.
For tournament games, there will be another Download button for tournament summaries. These are used to track your winnings, so download these as well.