As gunther said, your first time is generally a nightmare. I know that was the case for me. In fact, I think I quit trying the first day. I would advise anyone to practice setting up their hang on stands in the backyard before every attempting it in the woods. And practice doing it at ground level until you feel comfortable. Being 15 feet in the air just adds to the difficulty. There is one tip that I can offer that made a big difference for me. Take a thin piece of rope, about 8 inches long, fold up the stand, and tie the platform to the seat. I found that it was much easier to hold the stand to the tree while wrapping the chain around when the stand is folded up. Once you get the chain hooked on the other side of the mounting bracket, untie the platform, and lower it. This will tighten the stand to the tree a bit and should prevent it from slipping. (I should also mention that when I am wrapping the chain around the tree, I do not just go around the tree parallel to the ground. I angle it up the tree. This helps the chain grab on. I tried to draw a picture of what I mean) With the platform down, I make sure the stand has 4 points of contact with the tree ( 2 are made by the bracket below the seat, and the other 2 by the feet on the platform) If these 4 points of contact are made, I pound on the seat with my forearm to tighten everything up. Double check the stand to make sure everything looks ok and climb aboard while still wearing your safety system. Hope this helped and was not a bunch of gibberish! Its just as difficult to explain in words as it is to hang one! Good Luck!
My pursuit of a buck of a lifetime is much like the Chicago Cubs pursuit of a World Series...the season ends with a "wait til next year"