Add PIN to pre-existing Java app

I need to add a simple PIN code to my pre-existing app. The PIN code would be set in the app's activation screen which currently just stores a phone number. The PIN is to be stored in encrypted form using something better than MD5, preferably using bCrypt. It has a 'password' and 'verify password' field that it currently checks to see if they match, but since it doesn't do anything with it at this point, that can be removed. That's all there is to it! Please let me know if this is something you can do. Thank you, Tim G.