have been trying to make reservations on line for the several sites in Florence that require advance reservation (Brancacci Chapel, Accademia and Uffizi) The websites are not very helpful. I read that you can reserve in person once I get there in one of the sites that sell the Firenze card. Can I book reservations the day before I plan to visit. I should add, we are arriving early March. (In a couple of weeks)
For the Accademia and Uffizi, select the free ticket option in the time slot you want. You will have to pay the 4 euro reservation fee. When you show up at the museum ticket window give them your Firenze Card and the email with the reservation code. It's pretty simple. The Uffizi ticket agent even gave me the Accademia tickets for my reservations for the following day. Sorry, I haven't made it to the Brancacci Chapel yet, so I'm not sure if it will work the same way. I would definitely make the reservations in advance. But then, I'm not a gambler. Good luck and have a great trip!
Where is the free ticket option???
In addition to Jennifer's helpful response, take a look at the FAQ section of the Firenzevard's website as it answers a lot of common questions people have.
https://www.firenzecard.it/en/faq
For making reservations for the Uffizi, Accademia and Brancacci Chapel. scroll down to "Use" and click on "How can I book for the Brancacci Chapel", and "How can I book the priority access to Gallerie degli Uffizi and Galleria dell'Accademia with Firenzecard?". They note 3 different methods for the Accademia and Uffizi (only 1 for the Brancacci Chapel.)