Always, but always, paper away from the light source. Windows in particular. And soak, I mean soak. Paste 4 pieces and fold before hanging the first. In my case, wear your reading glasses and ensure that the seams are butted tight. Ignore top and bottom trim whist you are getting that right, it can always be peeled back and re-pasted as it hangs so as to be workable before trimming. That first piece next to the window needs to be dead plumb and the edge straight before to move on. Mare.