OK it's super easy. You'll need a short length of string, or a patient friend. The little wedge at the end is there to provide toe in when you set them up and quickly wear off. Some people don't like it and file it off, and use a piece of 1/32" thick cardboard as a toe in guide.

Set the shoes into the slot with the curve following the rim and the long end toward the back of the bike. Line up the shoes roughly and gently apply the brake and wind the string around the lever and handlebar to keep them on. You want them still loose enough that you can maneuver the shoes. Position the shoe exactly where you want on the rim, being sure that ti doesn't overhang where it might rub the tire. Jiggle it a bit to make sure the washers are settled home and hold it while you tighten.

Repeat on the other shoe, then release the brake and check your work. Lastly adjust the cable adjuster so the lever throw is how you prefer it and spin the wheel to make sure both sides don't rub.

You're all set, but don't be surprised by some brake squeal. It usually goes away after a little while, so instead of going crazy give it a chance to clear up on its own.