All you need to hang a hammock are some heavy duty bungee cords that are wide enough to go around the trees you want to work with and have a hook rated for the weight you need.
Ideally you want trees that are thirteen feet apart, but you can work within bigger or smaller distances you will just need to adjust the height of the hammock to accommodate it hanging higher or lower.
You want the two ends of the hammock to sit five to six feet above the ground so when you sit or lay it doesn't come too close to the ground.
Loop the ends of the bungee around the tree so it's snug against the tree and makes a tension point that will hold and support the cord. Repeat for your second tree.
Hook the ends of your hammock onto the bungee hooks and you're all set.
I would recommend checking your straps and hooks frequently to make sure they're not wearing too much, replace them as needed to keep your hammock safe, I'm Mrs. Fixit and it's just that simple!