You must define account segments in GP. This occurs during the GP installation process. You can view the Account Format in Administration>>Setup>>Company>>Account Format to see what segments currently exist in your install.
Whether you choose to use the full functionality of segments is optional. It might be helpful for you to read the Help files on account segments in GP. To do so, open GP, go to Financial>>Setup>>Segment. Open this window and click on the little blue Help button at the lower right corner of the window. You may find that some of the Segment functionality would be of benefit in the future.
