Make sure the paneling is clean and dry. Prime with a good stain blocking primer like Kilz. Then paint like painting regular walls. Acrilyc latex paint will work. If the paneling has grooves you can fill them with non shrink drywall patching compound. Just put on enough to fill the grooves. Let it dry overnight. Next day use a damp sponge to smooth the patch. Then prime and paint.
If you are tired of them ..Change their color!
The only instruction I would add to William's is to lightly sand the paneling before priming. If not, the paint easily scratches off. I've painted many paneled walls.