Thanks for the question, Sharon. That hoop (and the GH3 as well) requires the Quick Snap adaptor. The Quick Snap can be purchased at Embroidery.com:
If you don't want to buy that extra products I'd recommend one of the other hoops on this page such as the "Multi Needle Monster / GM3 8" x 12" (for use with arms)".
I hope this helps clarify.