If this is your first time shooting a bow and you're using fingers (I hope you are using a glove or pad) it could be the fish-tailing you're experiencing is due to plucking the string. You want the string to rest just on the tips of your fingers and imagine you're holding a pencil and just want to drop it. Pulling on the string before releasing (plucking) can cause the string to push to the side causing fish-tailing. Try just opening your fingers. What model bow is it? Give your form time to settle before you start tweaking settings.