If the branch is not too high you can tie something heavy to a light messenger line at least twice as long as the height of the branch. Maybe a kite string or butcher twine. Then throw the object up over the branch, with the line trailing behind it. This rather frustrating activity usually appeals to the male parent of the grandchild. Now tie the real rope to the messenger and pull it over. But the friction from a single rope over the branch can cause some damage to the branch. You can use the messenger line again to get several wraps around the branch to help spread the load.

Nylon ropes have a lot of stretch -- up to 50% depending on how they are made. So you should plan on having to adjust the height frequently. It is a good choice, though, because it will absorb shocks well and resists mildew and rot.

If you haven't already put the swing up, call a tree trimming co near you & see how much they would charge to do it for you....they may even supply you w/ the rope since you don't need that much. Good luck! :o)