Step 1: Make your stencil.
Photoshop (or any picture editor)
Find the picture that you want to use. Put it into Photoshop and carefully work around the edges of your reference picture. Erase all other color and make the emblem black. Also add bridges so that you do not need any islands in the stencil. Save the file as a .jpeg and then import it into blockposters.com. Print out the pdf file it gives you and start gluing them together, carefully trimming with your scissors to take off any excess. Once this is done you can start to very carefully cut your stencil out with a hobby knife. Now set your finished stencil aside until the painting part.