I think if you saw two lines in the video, the second one was for a tarp, and completely separate from the hammock.
The hammock should only have one ridgeline, and if it's tight, you need to adjust that by either raising the height of the tree straps, and/or loosening up your woopies/straps.
Also, make sure you are centered between the two trees. That was my biggest problem since the trees I was hanging on were on a hill...I was too close to one and it made that end of the hammock pull much tighter than the other end (which wasn't comfortable).
Practice, practice, practice. I set my hammock up and took it back down at least once a day for a week. I can almost get the hang perfect in the dark now.
Forgot to add: Welcome!