I think Mark has the right idea.
For Maggie's first several months, I always had treats outside with me and IMMEDIATELY rewarded her when she performed outside (I'm told this has to be aboslutely immediately as any later and the dog does not associate the reward with the desired behaviour). After a while, Maggie would go to the loo outside and then come up to me straight away for her treat, clearly expecting something after going in the right place.
We generally tried not to give her a chance to go inside - we took her out every 45 minutes and also swooped her up and took her out at the first sign of wanting to go to the toilet inside (sniffing, circling, etc). It's a bit of an intensive process but every time she went outside gave us an opportunity to reward her and now she's almost 100%.
If your puppy goes inside, I'd try to immeditaely pick her up and take her outside (perhaps with a sharp "no" or "uh-uh"). You might try to clean any mess inside with one of those products that masks the trace of the previous business but I'm not sure how effective these really are.
Hope this helps - good luck!