Hi there ,here's how you do it with epoxy: https://www.diynetwork.com/how-to/skills-and-know-how/painting/how-to-paint-a-garage-floor But I know there are definitely other products specific for garage floors; Paints, sealants etc.
Really think about it first. Once painted you can't go back. Friends of mine did it and hate it. Slippery, shows black tire marks had to recoat every 5 years. Just an fyi. They did the expensive epoxy coating, did look great in the beginning.
Concrete floor paint is just a tougher version of the paint that goes on walls and is by far the least expensive coating. You roll it on just like other types of paint; there are no tricky, unfamiliar steps. It’s also easy to touch up damaged areas or recoat the floor completely. Latex floor paint is easier to apply and clean up than oil-based paint. It dries to a low-sheen flat finish while oil dries to a high gloss. Oil-based paints must be used with a primer coat and are generally more durable than latex. Overall, floor paint isn’t as tough as other coatings and is especially vulnerable to road salts and other chemicals. Under typical conditions, you’ll have to touch up areas every year or two.
This tutorial should be of help: https://www.cleanandscentsible.com/paint-garage-floor/
This is a helpful video tutorial: https://youtu.be/CZvkBLTa6Ss
check that pin https://www.pinterest.com/pin/857021004077548082/
How other Hometalkers did it
We painted our concrete patio with great results. A few years later, rain, snow, ice, etc, and it still looks amazing. It's all about careful prep, application and the paint you use. Here's what we used and how we did it if you want to peek. https://www.exquisitelyunremarkable.com/2018/08/how-to-paint-concrete-patio-makeover.html
Buy a good garage floor paint from store, and Large paint brush, Roller with long reach handle. Paint around the perimeter with the brush, then starting from the farthest corner and working towards the door using your roller to complete the job.
There are lots of posts here:
Here's an idea:
This kit works well: https://amzn.to/3bUxQjC
Gray battleship gray is what you use for garage floors
Some instructions here:
There are specialty kits for this at your local home improvement store or a pro can do it.