This site has some great tips on how to put a topknot in and at the bottom of the page, you'll see advice on how to get your dog use to wearing a topknot. Just start with a band, and put it lower on the forehead to catch those short hairs, some people just use a mini clip at first.
Top-Knot How To's - The Diva-Dog Bowtique Your boy is adorable, and his hair looks long enough to do a topknot. Practice and upload a picture!