Set a ladder under the tree, and locate the branch from which you want to hang the hammock chair. Ask a friend to hold the hammock chair so that the bottom is approximately 2 feet off the ground.
Measure the distance from the hanging ring at the top of the hammock chair to the bottom of the branch you have selected. Add to that 8 inches to account for slack plus the distance needed to encircle the branch with the chain; you can determine that figure by measuring the circumference of the branch.
Purchase a link or coil chain with a weight rating of more than you expect to need; it is better to have too strong a chain than a chain that is too weak to support your weight and the weight of the hammock chair. Purchase the same length of chain and plastic tubing. Choose plastic tubing large enough to allow the chain to slip through easily.
Slide the chain through the plastic tubing, then climb the ladder and identify your branch. Encircle the branch with the chain wrapped in the plastic tubing.
Connect one of the end links from the chain back to the body of the chain using one of the quick links. Check the length of the remaining chain to make sure it extends far enough to just reach the hammock ring, then tighten the quick link.
Ask your assistant to hold up the hammock chair, then make any final adjustments to the length of the chain. Connect the end of the chain to the hanging ring on the chair with the remaining quick link.