To register a new instructor go to Planning -> Instructors -> Instructors Listing
You'll then see the next screen where you can see the list of instructors you have. There you can modify any instructor you have already created pressing on, you can remove them with. To create a new instructor press on New as it shows the next screenshot.
When you press "New" you'll see the next screen where you have to fill the next fields:
The basic information like Id Card, Name, Birth date... etc.
And you have to select also which classes this instructor will teach and the price you'll pay him/her for it.