To use the Map Provider URL you must enter a URL to a mapping website (Like MultiMap) along with some place holders (like {zip}) which will be replaced with the real content (Like Zip: HR8 2XL ) when the link is created in the listing.

So here are a few examples you can use:

For MultiMap UK: (If Post Code in address was HR82XL)
Using: http://www.multimap.com/map/browse.cgi?pc={zip}
would give: http://www.multimap.com/map/browse.cgi?pc=HR82XL


For MapQuest USA: (If Zip code in address was 90001)
Using: http://www.mapquest.com/maps/map.adp?zipcode={zip}
Would give: http://www.mapquest.com/maps/map.adp?zipcode=90001

Some times you have to play with Third Party URLs to see what varibles they accept, the above two are working examples.