If you need to prep the walking stick, this will be the most time consuming step. Usually, the bark will be easily removable with a knife. Smoothing the stick with sandpaper is the next step: start with a coarse grit to get rid of any large irregularities, and follow up with a fine grit to bring out the beautiful sheen of natural wood. There's more you can do to further polish up your stick, but we'll leave that for the variations section (later). If you mess up during any of this, or the stick proves especially troublesome to prep, feel free to use another one. Sticks are a free and renewable resource, after all.
After the initial prep work, the rest of this goes quickly. Gouge as small a hole as possible in the top of your stick that will fit the screw, using either a drill, a screwdriver, even the knife you used for prep work. Make it only deep enough that when the screw is inserted, enough of it pokes out that you can securely attach it to the tripod mount of the camera. Once the hole is gouged to the right size, insert some glue, followed by the screw and more glue. Make sure that the screw stays perfectly vertical! Once it's dry, scrape any excess glue from the top and adjust as necessary. Finished!