Jay,

Placement? Depending on the size of the pin, I could guess it might be centered 3 inches from the bottom and side of the apron. From there, adjust until its weight on the apron "feels" right. If the kilt is a tartan, you'll then want to place it on the pattern in a way that pleases your eye.

Look in the "Show us your pics" forum for the thread "Show us your favorite Kilt Pins." There should be enough to give you some ideas, but many of them are close-ups

The search feature was complaining because you had a word shorter than 4 letters---probably "pin." To search for that thread, try entering "show kilt pins"