If you want to create Regions for your League (optional), click on the Regions page, then click 'Add New'. Type in the name of your Region and hit Save. Your Region is now active.
When you create a Venue there is a drop down to select which Region to include it in.
If you select a Region and activate the Venue, you will see the Region listed in a drop down menu on your Leaderboards. The Leaderboard will default to 'All Regions' but will allow you to select the Leaderboard for any active region.