Hasbro Decals

It's a straightforward process, look up tutorials for the parts you get stuck on.

1] Learn to use image editing software. You just need to know the basics, tons of tutorials online for how to do things.
2] Buy water slide decal paper, check if it's the right type for your printer (inkjet, laser, etc.).
3] Find the images you want and resize them as needed. Simply measure what size it needs to be on the figure and plug the numbers into the editing software.
4] Print, apply, and you're done.

Alternately, talk to your local print shop and see if they'll do this small job for you. That's what I do when I need to print stickers because my home printer has bad print resolution.