While you are creating a listing for the pick-up item, when you get to the postage section you should have the option to create a new policy. If you click that, a window should pop up with options to name the policy, give a brief description, then select all the applicable postage options (in this instance, pick-up only).
It will automatically be applied to the new listing once you save, and will be available to select from the dropdown menu in the postage policy section for future listings.
