An essay can have many purposes, but the basic structure is the same no matter what. You may be writing an essay to argue for a particular point of view or to explain the steps necessary to complete a task.
Either way, your essay will have the same basic format.
If you follow a few simple steps, you will find that the essay almost writes itself. You will be responsible only for supplying ideas, which are the important part of the essay anyway.
Don't let the thought of putting pen to paper daunt you.