You will need two of each part, four parts in all. I printed them with 30% infill, and scaled them up by 250% 

You should have four parts to work with. You will need four small screws. Lay out the pieces so that they overlap and create the pliers. Thread the screw through the top piece and into the piece behind. Make sure that the screw goes all the way through both pieces, it is OK if it sticks out the back.  

Once you have all the joints connected, check to see if the pair of pliers close. If not, you may need to sand down the print. Where the pliers tips meet, towards the joint, will most likely need sanding. I just used a Dremel to sand it down quickly.