They make kits for that sold at Home Depot. Step by step instructions are in the kit. Prep is very important. Just know once they get scratched they will peel, but the kits are your best bet for lasting A few years.
Yes, and you need it, not so much for the ceramic element as for sealer and gloss. Ask for recommendations at your local paint and home improvement stores. You will find whole lines of ceramic paint, but make sure you get ceramic FLOOR paint. I like Lowe’s for paint since I’ve always gotten good advice there. Best wishes, ☺️
How you paint them also depends on where they are - bathroom, living room, etc. Which floors are you planning to paint?