I love my tree wall! It was super-easy to install!
The decals arrive arranged a on piece of paper, I used the diagram on the package so I you could figure out which branch goes where. The leaves can be placed any way you like. You start with the bottom trunk then It's easy to tell where each branch attaches, and the diagram on the package makes it easy to set up. Start by peeling off the bottom edge, aligning it where the branch comes off the trunk, and then slowly un-peel the decal, rolling up and away from the trunk. I used a driver's license as a straight-edge to smooth it to the wall as I unpeeled the decal.
I did find that any lumps and bumps on the wall stand out if the decal covers them, and there is a slightly visible stripe where I overlapped pieces by maybe an eighth of an inch. But these are only noticeable if you're standing right next to the wall, peering closely at it. It doesn't leave any marks on the wall or paint, although I suppose if you take it down after a few years, the wall might be cleaner where the decal had been.
All in all, this decal makes me very happy. It was kind of fun to put up, and I love looking at it. Everyone compliments me on it, and I seem to have become a vinyl wall decal catalyst. All my friends want decals now.
Tip: Place the leaves where you want after you hang your framed pictures.