Start by trying it out in your garden og someplace close to your home - BEFORE trying to set it up in the middle of the night at an unknown campsite...
Hold on the the ropes and /or side panels (not the mesh pockets!) inside the hammock. Take a step backwards so that you are both along an imaginary line between the trees. Stand to each side of the hammock and push the hammock down and forwards, while you try to sit down in the middle of the hammock. If the hammock is too high - consider lowering it a little.
Watch this video.