In Step 4 of 4 in the "Please verify your registration information before submitting" window, the following appears:

GUESTS PRICE UPCHARGE ITEMS PAYMENT METHOD
Jim Ladner $55.00 Paypal

What does the reference to "Upcharge" here mean -- and how does one implement an "upcharge"?

That column refers to if you had set up an item, such as a Menu Option that would have cost more, that there would also be an upcharge that would have been listed in that location. For example, you may be serving Chicken for your base price, but had an upcharge of $5.00 if the member wanted to opt for Salmon.

Thank you for your input.

I was not able to find out where one would include such an upcharge -- that is, how one would go about doing so.

Is that mentioned somewhere in the FAQs (if so, I missed it)

In the Edit Event page, there is a spot that asks if you have Menu options. If yes, the system expands and allows you to add your options and their prices.