For new mobile edition you still need to feed it raw fish meat (prime is better) to tame by placing it in the last slot of your tool bar and walking over to the otter. Once you get close enough and see the message “drag a fish to feed” click on the fish meat in your tool bar to feed.

With the new version however this won’t tell you when the otter is hungry again, unless you actually drag a fish with you while doing this. You won’t be feeding the otter the dead fish, still the food in your inventory, but this will show the “wait till hungry again” message until it is hungry. dragging a dead fish isn’t necessary, the feed timers stated here still appear to be accurate for its feeding intervals, so I just pay attention to time rather than trying to swim around while dragging a fish. Remember the first feeding interval is longer!