Usually you would be taught how the machine operates compared to other types you've maybe flown. You would need to learn the systems, and cover all type specific emergency procedures. ie, you may have never flown a machine with hydraulics before and you'd need to experience failure of them.
In the UK, you would do a theory section with written exam for type. The training takes a minimum of 5 hours if converting to another SE type or minimum 8hours for first ME type.
There will be a skills test at the end of the training.
You'd possibly be taught the walkaround and what to look for.
You'll find most FTO's or TRTO's will have a conversion manual to go through which covers all elements required before test.