After you've added nodes to your hierarchy and assigned accounts to them, you can create up to two custom descriptions for your account numbers. You can also edit these descriptions using the Tree Builder screen. Select the node you want to edit, and then click Edit Descriptions. Make your changes or additions, and then click Save. (You can also edit sub nodes using the same screen. If you don't immediately see the sub node you want, try clicking the plus (+) sign to expand the branch.
If you haven't created a hierarchy, you won't see the edit levels option. You must create a hierarchy and make it active before you can add nodes, accounts, or services to it. To figure out which hierarchy is active, click the Set Hierarchy link on the Setup page.