Making cement look glossy
The most important thing you need to do is prepare the surface properly, which means removing all existing coatings and/or foreign material from the concrete surface then etching it with acid. if you are comfortable undertaking this yourself, there is a lot of online information and tutorials. Follow the preparation instructions for the coating you choose to the letter.

After thorough prep you would use epoxy concrete paint. It is a specialty coating requiring special application techniques. There are concrete paints available that are designed to look like marble when applied properly. Use your Google-Fu, check this link: marble floor coating kits, then go to a reputable paint store to gather even more information.