google has rules for free users that they cannot use it for commercial purpose's but u can use it if you are building for fun.if you realy like it and want it you can by it for commercial use
here is the first few steps to get it done
goto http://code.google.com/apis/maps/ and there will be a link called Sign up for a Google Maps API key.
to get this feature you should own a gmail account because you have to sign up using you gmail account
then they will give you a API key that you will use in the code to get the service
And please read the google terms of service before you use it http://code.google.com/apis/maps/terms.html