If you wish to enter multiple items you must fill out an entry for each item. If you select "Submit an entry" or "Notify intention to sell" you will also be asked to fill out a volunteer roster. If you have already filled out a volunteer roster, indicate this on the Volunteer page. If you just wish to volunteer for a roster choose one of those two options.
"Submit an entry" will give you the option of proceeding to Intention to sell.