To start creating divisions click Divisions at the top of the page
Then click Add New Division, or Bulk Add/Edit Divisions
Next you'll enter in the divisions info such as Division Name, Division Abbreviation, Gender, and Schedule Color (used to distinguish divisions on the drag/drop page). Enter the info that applies to you and hit Save.
Now your division will have its own tab with options for adding pools, teams, generating pool games, creating brackets, and adjusting the division's info.