In order to inject hydrogen into your motor, you have to make sure you have an electric powered motor in your car. A traditional gas combustion engine will not work.
Make sure you have a hydrogen storage tank. Hydrogen is stored in a specialty tank that can hold it at very high pressure to give you a longer driving range. This is also one of the dangers of a hydrogen-powered car.
Have a power control unit that will manage the amount of the electricity that is distributed from the engine.
You will also need to have a fuel cell tank, which is what will convert the hydrogen and the oxygen into electricity for the motor.
You will also need a high-output battery that allows you to recharge the battery during braking. This allows your car to run more efficiently and generate more power during city commutes.