Your essay this week is "Convince a friend to follow a healthier diet".
Pay attention to the keywords:
convince (give reasoned arguments), a
friend (informal style, you can use contractions)
healthier (that means that your friend already follows a healthy diet so you have to suggest how to improve it), and
diet (only his/her diet, not lifestyle).
To review writing a composition, have a look at these two links:
Composition structure and
Composition Writing: the main stages.
I've found this video that also give you some ideas:
Have a nice weekend.