There are two factors in hitting the ball harder:
1. bat speed (the faster you swing, the harder the ball will come off)
2. The efficiency of contact (matching the plane of the pitch and creating a "head-on" collision is more powerful than a chop swing that clips the ball). However, this is mechanical, so I will let this be and focus on improving bat speed.
To improve bat speed, as Dominik said, you must have the intent to swing hard. Especially right now in the off season, you can spend time focusing on that.
I recommend getting a blast sensor and paying the $60/year subscription so you can see all the metrics. By having a blast, you can track your bat speed and see if you really are improving the speed and make adjustments to see what's working and what's not.
I'm also a big fan of overload/underload type stuff, but they are pretty expensive. You could either buy them or add some tape to an old bat to make it an overload. No matter what it is, though, swing as hard as you can and have the intent to do damage.
BUT ABOVE ALL GET BIGGER FASTER AND STRONGER. THIS WILL BE THE MOST BENEFICIAL FOR YOU. I also didn't realize you were a 2025, so the finances may not be there to pay for blast/ overload underload bats. Get a gym membership, workout a ton, eat a ton, and whenever you swing a bat, swing it at near-maximal speed.