While working in your AWeber account, each task is list specific. You can easily toggle between lists by using the "Active List" drop-down menu at the top-right of your account.
You can also use the "Search lists" box to type in the name of the list you'd like to select:
Note: If you do not see this option, you are likely in the "Lists" section. You'll see all of your active lists under the "Email Marketing & Analytics" section. Simply click on a list name, and you will see the "Active List" drop-down menu at the top of your account.