i have to write my teacher instructions on how to do something but what?

How about a recipe for your favorite food? or a math problem, or online shopping and ordering, or recycle properly, making a facebook account, how to obtain and maintain good credit, or if you have a job then something about that, how to make a bed, how to match an outfit, how to pick out a great wig or get your hair braided, how to start an online business (ebay or etsy), or how to write a good research paper.

I hope this kick-started your thinking process!