How to find a pool leak?

My daughter put up her above ground pool (5’deep x 10’wide w/plastic liner) this weekend. There is a leak. She filled it approx 5″ deep and there was a trickle of water onto the ground tarp that is under the pool and extends approx 2′ around the pool like a sidewalk. Today there is no trickle, the tarp is dry and the pool has approx 2 to 3″ of water in the bottom. Any suggestions for finding the leak? Any help will be appreciated. Thank you.