Writing instructions normally tells us how to do something. Writing instructions is a skill that you should try to perfect. If your instructions are not clear, you might cause loss or damage to someone. In serious situations, the wrong instructions could lead to death.
The best way to write instructions is by using the imperative mood: this just means that you use the dictionary form of the verb to give an instruction, e.g. 'Stir slowly for two minutes'. 'Stir' is the dictionary form of the verb and is used as an instruction to do something. Here's another instruction: 'Don't add more than 250 grams of raisins to the mixture'. 'Don't add' instructs you not to add.
Try this 11-plus English quiz and see how well you do with giving instructions. Don't forget: instructions can be both written and spoken.