For me it is dry but the graphic is warmed up first to make the glue want to stick. I cut a small section all the way through the backing, from top to bottom, so I can place the graphic and only adhere the middle part. But I only do the center of the exposed adhesive to start and then make sure my alignment is correct. After that press on the rest of that exposed line of adhesive. Then I pull paper backing from the center out all the while working any bubbles out as I go.
This method makes it so no bubbles end up being in the middle.