Training to jump higher is not easy if you don’t know what to do and what to aim for.
Generally you want to increase your strength and quickness.
You need the strength in order to have the physical capacity to actually lift your body weight under extreme pressure.
And you need quickness in order to be able to move fast enough to create an explosive motion that allows for you to gain the needed vertical.
In the gym you will find several exercises that are great for this purpose.
For instance, you have dumbbell alternating jumps, squats, lunges with dumbbells, jump rope exercises and much more.
Don’t forget the box jumps and other plyometric exercises as well.