Do a little Jelquing, or try Male Extra (more information available HERE) in order to get extra blood flowing to your organ. This is optional, but will help speed up the process. The key to most muscle and tissue recovery/growth is making sure the cells are getting oxygenated and receive the proper nutrients. Blood carries all of that to the tissue, so the more, the better.
However, after more than a century of generally dubious and sometimes lunatic penis enlargement attempts, there's still not much you can do. Sure, there are lots and lots of supposed options out there -- penis pills, creams, brutal stretching exercises, horrific-looking devices, and penis surgery. Almost none of it works. The few approaches that can work often have modest benefits and serious side effects. How serious? In some cases, erectile dysfunction-serious.