How Do I Write An Essay For A Company I Applied To For A Job Telling Them How I Can Fit In?

First off think about the company that you have applied to, do some research, read up on the internet about the type of company and think or consider which types of skills, attributes and personal qualities are required to do that particular job.
Once you've made a list of those, begin your essay.

Introduce yourself simply, I am Sasha, I am twenty years old, I am a trainee Sales Manager, or Recent Graduate of such and such college or university.

Then go on to tell them how you feel that your skills, attributes and qualities match what you feel they are looking for.  If you can get hold of a job spec (specification) or description, then that's even better!

Try to think of examples in your life, studies and work experience that you can use as a examples.  

An example of when I used my initiative is when I worked out that a website would triple my number of sales per month.  This earned me a promotion.  (It's good to put a result next to it).