After you beet ravenscar you will talk to the king of grizzleheim. then an icon will appear for you to talk to ambrose. after you talk to him you will have to talk to the king of grizzleheim again. He will tell you to talk to a guy in ravenscar. Then you will talk to the king again. He will tell you to talk to baldur goldpaws in grizzleheim. he will then take you to grizzleheim.
(p.s. to get into revenscar you have to beet a quest that has you fight a guy named jotun. it will not be easy.) and to get that quest you have to be level forty.