Final Project Java Class- Don't know where to start.

Hello there-

I am trying to build a foursquare web app that when a user logs in they can see where they have checked in with friends in the past.

I understand the process i need to code: -get permission from the user (OAuth) -search their check in history for checkins with friends -return gps coordinates of checkin and profile picture of friend -display picture on gps coordinate on a map

I have the authentication code and list of endpoints but I can't get the authentication working and am hitting a wall.

Any suggestions would be greatly appreciated.