If I am 15-20 feet up in a tree how do you you aim with the fixed sights on a ML , I am a planning on a 6'oclock sight in and should I just settle the bead just under the lungs - brand new game for me guys so wanted to head off mistakes before they happen

Shooting from a treestand with a ML- aim like you normally would. Now when bow hunting, you need to compensate for height, but at normal muzzy ranges you don't need to worry about it. Now if the deer shows up right under your stand and you are shooting at an extreme downward angle, you have to take in consideration what path the bullet is going to take thru the deer. For example, in this situation, you don't want to aim too low- the steep angle might make the bullet miss vital organs.

For example, the buck I took last year was underneath my stand, quartering to me sharply. So I aimed for the top point of the shoulder facing me - the bullet entered there and travelled at a downward angle thru the lungs and exited the lower chest on the off side. So just keep in mind when shooting at steep angles, and think where the bullet is going to exit so you get a good solid body shot.