Welcome, FlapDragon!
I can tell you that after a lot more practicing, you'll find that making one hand louder than the other becomes not only easy, but necessary to playing many pieces correctly. Not only one hand over the other, either; you'll soon be working to make one NOTE out of a chord sound louder than the others, also as a common-place requirement for a good performance of many pieces.
So, where do you start? It's ALL about listening to the sound you're producing and CONCENTRATING! Of course, it's also about controlling your fingers, hands, arms, and shoulders. But the trick is to exercise control while keeping yourself relaxed. Yes, it's easier said than done, but this is where practice comes in.
With this challenge (making one hand sound louder than the other), at first, you can exaggerate the volume of one hand over the other by addressing the chord you want made louder by consciously using MUCH more force with that hand and holding back with the other. After you "get" that technique, you ought to try to make one hand just a LITTLE louder than the other, thereby gaining control.
If you can practice even a little every day, you're better off than practicing a lot one or two days a week. Every day you listen to yourself making the piano speak (while always intending to make it sing), you will make some progress, even if it's hard to notice at first. Part of the reason for this is that your body learns things your mind is not even aware of it learning! After a period of time practicing regularly, you will find things that are now impossible seem easy or at least MUCH easier.
Good Luck!
Bruce