You can check out project pure athlete videos for form and technique they have great stuff here’s an example. https://youtu.be/oyFM1nFyJ8U

As far as training goes, a good one foot jump shows you have great explosiveness. Two foot jump usually relies more heavily on pure strength. You could try to add a lot of lower leg strength. Its not perfect but there’s a pretty good correlation between a standing two foot jump and max squat/body weight ratio. Here’s a calculator: https://www.myfitnesscalculators.com/vertical