Summarize the following:
To ensure the glue you use doesn't cloud the surface of your puzzle, flake, or cause damage, you should use specially intended puzzle glue for gluing your puzzle. This can be bought at most craft and hobby stores. In all, for this project you'll need:  Puzzle glue Paintbrush (or sponge) Parchment paper (or wax paper) Any clear adhesive, like shellac or decoupage glue, can be used to glue your puzzle together, though some glues might leave a cloudy finish or not glue as firmly as puzzle glue. You'll want to work on a level, clear space while gluing your puzzle. Sometimes, glue can seep between puzzle pieces, causing the pieces to stick to your work surface. To prevent this, you should put a layer of parchment paper between your puzzle and the surface on which you're working.  The parchment paper you lay beneath your puzzle should extend several inches beyond its outer edges. If you don't have parchment paper handy, you could also use wax paper to prevent puzzle pieces from sticking to your work surface. If you are able, slide your puzzle over the top of your parchment paper. If this is not possible, you may need to get a thin, stiff piece of card stock to slide underneath your puzzle to help you transfer it to the parchment paper. At this point, your puzzle should be facing picture side up atop your parchment (or wax) paper, and your paper should extend a few inches beyond the outer edges of the puzzle. To ensure an even layer of glue is spread over your puzzle, you should start at the center of the puzzle and work your way to its outer edges. Start with a moderate amount of glue first. You can always add more later, if necessary. Working from the center of the puzzle out will also help prevent you from using too much glue, which can cause unevenness in the glue. Add your glue a little bit at a time and use your paintbrush or sponge to spread your glue from the center to the outer corners of your puzzle. You should only need a thin layer of glue to hold the puzzle pieces together.  Adding too much glue to your puzzle can sometimes cause the pieces to curl when the glue is dried.  Some brands of puzzle glue come with a plastic glue spreader that you can use to distribute your glue over the surface of your puzzle. If you find that a brush or a sponge doesn't work well for spreading glue and if your puzzle glue did not come with a spreader, you may be able to use a plastic spatula to distribute the glue more quickly. However, dried glue can be difficult to remove from your spatula once you are finished. In many cases, when you reach the edges of your puzzle, you'll find that you have some excess glue. Remove this by pushing it off the edges onto the parchment paper with your paintbrush, sponge, or plastic spreader. If you are using a plastic spreader/spatula, you may be able to remove extra glue by scooping it up and wiping it onto a piece of paper towel. Depending your the brand of puzzle glue you have bought, this may only take a few hours or may require an entire night to dry. When waiting for your puzzle to dry, it's best to err on the side of caution. Moving your puzzle too soon can cause wet glue to deform the puzzle pieces. You should check the label instructions for your glue to determine the amount of time your glue needs to dry.

Summary:
Acquire your materials. Lay out parchment paper over your work area. Position your puzzle on the parchment paper. Add glue to the center of your puzzle. Spread the glue evenly over your puzzle. Remove any globs of glue from the puzzle. Allow the glue to dry.