The setup for the Dynamics GP general ledger is pretty easy. You will want to make sure you have a Retained Earnings account specified, and that you have marked to Maintain Account History and Maintain Transaction History. You can select to be able to post to prior periods, but you may want to wait on this one until you actually have to post that type of transaction. You can check it “off” and check it “on” as you need.
This video shows the minimum general ledger setup for a new GP company: http://youtu.be/cb6q7ew9jxQ