The text-based tutorial should explain the task in a step by step fashion using text and pictures.
For each step...
you should provide a complete explanation of that step of the task.
you should include a picture or image that supports the text for that step.
Your instructions should be clear, concise, and complete.
Use proper grammar, correct spelling, and great sentence structure. The Tramalfagorians are just learning English and we do not want to confuse them.
The tutorial should be creative and engaging.
Ultimately, a person or alien who is approaching the task with absolutely no understanding should be able to complete the task if they follow your text-based tutorial.