As usual for practical training, normal practice is to get the trainees used to the machine driving controls and then to train them in steering techniques before starting on the hydraulic functions.
This would include accelerator and brake along with inching pedal and gears. The handbrake should also be covered along with any range change levers.
Almost all telehandlers have steering which can be set to normal, four wheel steer or crab steer and this needs to be explained to the trainees.
As mentioned above, the instruments and gauges should be covered in detail and the trainees taught how to use any cold start system that may be fitted to the machine.