First, you have to get <iframe> from maps.google.com/. Please click the mouse on your address, zoom-in to see your address clearly. Please click the ‘Link’ and copy <iframe> in P’aste HTML to embed in website’ field:

Then, please paste the code to default file of Contact component (Sometime, we need customize css, so you have to find it in: yoursite\templates\sj_template\html\com_contact\contact\, if have not com_contact folder in html folder, please go to default in: yoursite\components\com_contact\views\contact\tmpl to find default.php)

Maybe, you have to customize css to it display properly.