To complete this task return to Kakariko Village. Pikango will be waiting for you in front of Lady Impa's house (1). Talk to him and agree to help. In the vicinity of the Ta'loh Naeg Shrine your companion will become tired and will ask you to continue alone and take a picture of the fountain.
Keep going forward. Approach the inactive fountain in the forest (2). You will get a proposal, that for 100 Ruppee, you can start using the fountain. Agree, and then take a picture of the Great Fairy Fountain. Return to Pikango and show him the picture, after that the quest will be completed.