Selectors define who or what should qualify for Lists, Filters, and Reports.
Drag fields from the Library or click the plus icon to add a filter to your Selector.
At any time, you can use the Calculate Members button in the top right of the page to see the number of members that would qualify based on the current filters added to your Selector.
When finished editing the Selectors and logic, click Save.
Now take a look at the list tab to see what qualified!