The process is very easy!
To enter and select your zips:
Simply head to your 'Update My Profile' page and look at the top section called 'Zips you Cover'. Enter the zip in the input and click the orange button to add it to your pool of zips (these will be GREY).
Then, from your pool of zips, simply click on the ones you'd like to be featured in (they will turn ORANGE).
To change your zips:
Click any of the featured (ORANGE) zips which will turn them back grey and select another one of your zips in your pool. If the zip is not already in your pool, add the zip in the input just like you did above.
Keep in mind that each account is limited to the number of zips you can be featured in.
Basic includes ONE zip.
Professional has THREE zips.
Premium has SIX zips.