Before you do anything, take a 2' x 2' piece of thick plastic and duct-tape it to the concrete floor completely on all 4 sides. Then, after a few days, see how much moisture comes up from the concrete. If it's just like 'dewy', then you can seal and paint. If it's more like raindrops, I wouldn't do it. You see, concrete will absorbe moisture and breathe it out. This can be harmless if it's minimal.
Assuming you have a dew-like film under the plastic, go to your local Paint Retail Store (found in the Yellow Pages under PAINT - RETAIL) and tell them what you want to do. THey'll give you a sealer for the job. DON'T skimp on the material. Buy good 'tools' too. Cheaper products are available but you get what you pay for. (I don't think you're interested in re-painting every 5 years, are you? If so, go cheap.) But remember, now that you've painted your floor, you've transformed a maintenance-free 'item' into one that now requires periodic maintenance.