Rome & Florence

In its current form you question doesn't give us enough information to respond meaningfully.

Not trying to gin up business for Rick Steves, but suggest you start by purchasing his Italy 2018 guidebook and then begin to digest it to have a better idea about what you want to know. Most of your questions can be answered from the guidebook, and then you will be focusing on the other issues that we can address for you.

https://store.ricksteves.com/shop/p/italy-guidebook

How early are you arriving and what is your schedule after Florence?

You're going to be in Rome and Florence for a day? ...huh?

Please be a bit more descriptive about your trip/time.

Not knowing your budget I would recommend the hotel below. It is right across the piazza from Santa Maria church. Very nice hotel and breakfast with a great view of the church. Walking distance to the train.

http://www.hotelorologioflorence.com

After in depth consultation with my crystal ball this is my take on what OP is planning and asking.

We are doing a tour which begins in Rome. We arrive in Rome early the day before it starts and plan to go to Florence and spend the night there and then return to Rome the next day to join our tour. How do I get from FCO to Florence and what hotel near the Florence train station do you recommend? How do I do the trains?

Note, I got my crystal ball at a yard sale so its out of warranty. The real situation and question may be a whole different animal

To look up trains, use this.

http://www.trenitalia.com/tcom-en

You need to use Fiumicino Aeroporto-Firenze SMN as your departure and arrival stations.

There is a direct train that leaves the airport at 11:08, takes 2hr20min. Otherwise you will need to change trains at either Roma Termini or Roma Tiburtina station. These trains add at least 1/2 hr to your travel times, not including wait time for a connection. Trains from Florence back to Rome are at least 90 min.

You need to consider if the short amount of time you have in Florence is worth the trip. Since you may experience jet lag, and end up just sleeping and wandering around in a haze the next day.

My crystal ball is telling me the same thing as Joe's - tour starting in Rome on day 2 and spending arrival night in Florence.

Trains are super easy. Upon arrival at FCO, go to Trenitalia ticket window at the FCO train station and buy tickets to Florence SMN station. There are multiple departures per hour, with 2 direct trains per day (but don't wait hours for these) and the rest requiring a change at either Roma Termini or Roma Tiburtina. For your return train to Rome, buy tickets to Roma Termini. If you know what time you want to leave Florence, you can buy discounted tickets online for Trenitalia or Italo trains up to 120 in advance. Savings can be as much as 50%, but note that discounted tickets come with restrictions. Make sure you read and understand the restrictions before buying online.

Only one day in Rome? Confusing post.