I did not find any product or technical information on the Hoover model number that you submitted (F906-900). The image below shows how to connect the upholstery cleaning hose to one type of Hoover Steam Vac. Maybe this information will help you.
If not, you can recheck the model number and search for the owner's manual for your unit on our Manage My Home site or on the Hoover website. Here is a link for the customer service page of the Hoover website that contains an owner's manual search feature:
Hoover Customer Service Page
If you need more help, resubmit your question with additional details and the full model number of your Hoover Steam Vac (after rechecking the model number).