Since 3.9.0 version every Address field has a corresponding Map field. All you need is to put it on Detail layout. It uses Google Maps service.
Administration > Layout Manager > Choose entity (Account, Contact, Lead or custom one) > Detail > Drag & Drop Map field.
Make the cell wide using the minus sign.
You can also configure the height of your field.
Administration > Entity Manager > Choose entity > Fields > find the map field and click on it > edit the height and save.
Since EspoCRM version 4.2.0 you need to specify Api Key to use Google Maps (Administration > Integration > Google Maps).