We trained my dog to do that. We hung a set of bell and when he wanted to go out he would whack them with his nose. You can always carry him out at certain hours and let him sniff and when he goes potty reward him.
It does work with patience. I got Sam from the humane society when he was 7 months. They said he was trained but he wasn't. So I put bells on the doorknob and everytime I took him out for a pee I rang the bell and before long he was ringing the bell when he wanted to go out. Good Luck.
Make outdoor "going" a rewarded behavior with lots of positive praise and perhaps a treat. Ignore the indoor going. Bells are a neat accessory, but they don't help per se.
you can try taking the dog out on a daily routine/schedule. use treats and a catch phrase such as "big boy" at potty time. when he goes, say "big boy", immediately give the treat. after a couple days you can encourage him to go by saying "big boy" once in a while.
food is the great motivator, so it won't take your puppy long to associate going to the bathroom with getting his praise and a treat.
i would work to continue the schedule for up to six weeks. as the pup gets older, you will notice he won't have to go to the bathroom as often.