Well, first thing to do is to get the part of the tree that broke off (the big branch) loose from the part of the tree that's undamaged. Start with a down cut on the top of the broken section in near where it split. About 1/2 way thru is good. Then make an upward undercut (use the top of your chainsaw bar) to finish cutting the split off part free. Remember, cut from the top first then finish by cutting up from the bottom to keep your bar and chain from getting pinched. Chances are really good that the split off part will just fall straight down into the ground when you cut it free. But, I'd clear a path and plan to get out of the way just in case. As you're cutting pay attention to what the broken section is wanting to do as you're finishing the cut. After you get the broken section cut free it'll probably still be hung up in the other tree. Easiest thing to do is hook a rope to it and pull it free with a truck ideally. Shouldn't take much to get it out and all of it safely on the ground. If you can't pull it out then cut the branch at a comfortable height for you. Top down first, up from the bottom second. Repeat as needed to continue to shorten the broken branch. Definitely plan on running out the way because at some point the part that's hung up in tree is going to become short enough that it could topple over back towards where it came from. I hope this helps and best of luck. You can do, safety first always. And no cutting up on a ladder!