Zip/Postcode search only

Hi all,

I’ve been trying to figure out how a guest visiting my website would be able to make a search via “postcode”. For instance, they would input their own zip/postcode and the listings would appear in their desired radius.
As it currently stands, inputting a postcode displays all listings regardless of the radius set. I’m also having an issue with “distance” under each listing, entering your own postcode doesn’t seem to register on Google Maps, resulting in distances being way off.

How do I make a search via postcode to display listings only in a certain radius? And make it so a user inputting their own postcode would have a correct distance from one of the listings.

Help woud be greatly appreciated. 🙂

Thanks