The things you can use to attach them are called doodads. I had a link to a supplier but can't find it now, of course. I'll do more digging but I may have deleted it because they didn't ship to Canada. I've seen some sellers on Etsy selling them, I'm sure they'd be on Ebay as well if you want to see what they look like. To me, the part that attaches to the bow looks so small, I'm not sure how well it would hold.
I've also heard some people use alligator clips to slide through the holes, but I found that french clips (the smaller ones) work great! They slide through the holes and hold really well because they snap closed. Any of the pokey parts of the clip are on the top of the shoe so they wouldn't hurt the foot.
If you scotch guard the korker beforehand it'll be easier to keep clean too!
Here's a link to what they look like. http://no-plain-jane.com/catalog.php?item=237
I just googled and that's the first thing that came up.