Kris, all you have to do is put them in a glass or a jar with about 2 or three inches of water. You want to remove any leaves that would be under water so they won't rot and cause the roots to rot. If there are any blooms cut them off so the plant can put all it's energy into producing roots. Change the water every 2 or 3 days. You'll should have roots in just a few days. Coleus is one of the easiest plants to root.
Good luck

Hi Kris,
I have rooted many plants, geranium, mums, forcynthia, hydranga, coleus etc. I use an old window box liner and fill it with wet sand. Put the box in a shady spot and keep it moist. In a week or so (depending on plant) you'll have nicely rooted cuttings. Hope that helps,
Betty

If you are using a container with a wide opening you can take electrical tape or any heavy 1/4" tape and make a criss cross pattern over the opening. That will give you a small spot for each cutting and will keep them in place.