It's easy to create a list using the SuppressionList UI.
Begin by logging into SuppressionList then making sure you've clicked on the "Lists" tab. If this is your account's first list, you'll see a "Get Started" button. Or, click on the "+" button at the lower-left corner of the screen. Give your list a name, and click "Create List". That's all there is to it!
You'll see a screen with information about your list including: It's internal List ID code, its URL Name, and the list's API Key.
Once you start making queries to your list, activity will be displayed in the "Usage" area.
From this screen you can also configure or modify Automatic List Pruning for this list.