When you're being someone's dom they don't get a dominance meter, they get a submission meter. Make sure the person you're dating has the submissive inclination and it helps if they have a naturally submissive personality (insecure/passive/etc people are easier to make subs than confidant/forward/etc people).
If you mean you wanna raise your assertiveness/dominance skill there admittedly aren't a lot of avenues for that afaik. The only ones I can think of are raising your physical skill so you can steady/grope people on the bus, speak up for people getting bullied in class, find someone with the submissive inclination and dominantly flirt with them in the evening, and glare at people who ask you to smile on the street. Or you can use cheats.