To use Google Maps in mojoPortal content management system, you need to get a Google Maps API Key, and then you can enter this key in mojoPortal under Administration > Site Settings > API Keys.
Alternatively, you can put your Google Map API Key in Web.config/user.config like this:
<add key="GoogleMapsAPIKey" value="xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" />
If specified in Web.config, the setting there will trump any setting from Site Settings. Using the Web.config setting would not a be a good idea if you are hosting multiple mojoPortal sites in the same installation. in that scenario using the Site Settings is preferable so that you can enter an API Key separately for each site.