Put your jumper on and using tailors chalk mark crosses where your elbows sit. Take off your jumper and measure down from the cuff/top of shoulder to mark the same positioning on each of the arms.
Cut a pattern piece so that your patches will be even and cut out your fabric to roughly the right size. I chose a small floral Liberty pattern to make a statement, but you could use any fabric you like.
Iron on some bondaweb onto your fabric. Remember the glue side goes onto your fabric and run the iron quickly over the bondaweb sealing it on.
Using your pattern piece draw it onto your bonadweb.
Cut this out. I choose to use my pinking shears to cut with to give a nice edge to the patches.
Peal off the bondaweb backing.
Iron each patch onto your jumper into the positions you have marked with your tailors chalk.
You can also use embroidery thread to go around the outside of your patches to ensure they stay in place or just leave them as is. Then you are done.