I discovered PicMonkey only about six months ago. Yes…I’m a little slow coming to the party. This software program allows you to do SO many things, including adding overlays to your images. I’m listing below a recent tutorial which gives virtual step by step instructions on using the Overlay tool and all the wonderful things you can do!
From the PicMonkey Blog:
Crown your cat! Or, mustache your baby. Label it, logo it, and embellish it. Think of overlays as sophisticated photo stickers. And we’ve got a feast of them in the Overlays tab. This video primer will make a beginner proficient and an expert a little more expertly. Learn how to change color, resize and play with the overlays you add to your images. Or, get the professional advantage and add your own overlay or watermark to your photo. This tutorial’s got it all.
To check out the original tutorial and other awesome tips by PicMonkey, go here.
Blessings!
Vintage Scrap Shop 
Hi Stacy:
I am IN LOVE with picmonkey! Thanks for sharing the tutorial!