I took some metal use sandpaper and scratched up the pen barrel where the leather will be attached to. After I took some master's Contact Cement and applied a coat to both the Leather and scratched barrel. I allowed the glue to dry and become tacky before joining the pieces together.
If you remember that I suggested that one side be skived thinner for the glue over to prevent it from being bulky. If you look at the second photo you will see why I mentioned it.
Once the leather is wrapped, I use my finger to rub up and down on the leather to make sure that both the leather and barrel make good contact. I also use my finger or gum eraser to remove any residue glue from the fold over joint.
From here, all that is left is assemble the pen project. It will take some elbow grease to do so. I want to caution you, if you deploy any time of hammer. Do so with extreme care and light force. You can easily ruin the interior pen mechanism. Trust me!