I am into my new Harmony 550 for about a week so I understand your confusion. If you step through the wizard, you may have an option that says "I don't need to set an input". Choose that one. When I set mine up with my 722, I added an input and called it HDMI. Everything is working fine with this setup. I don't think you'll have any problems by selecting the other option since the 722 only has one input.

Hope that helps.