I mean the introduction. Does it have to be very long?
Here are a couple of excellent sites on writing introductions to essays.
Generally speaking, a good introduction would have minimally 5 or 6 sentences. However, I think the key to the introduction is that it is attention getting. It is the "hook" that makes the reader want to continue. Say something that is relevant to the reader that makes the topic important. Give the background for your interest and write a good thesis.
We will be interested in seeing your entire essay and one of the teachers will be glad to make suggestion.
A thesis statement is one sentence used to clearly state what the paper will cover.
I also searched Google under the key words "introduction length paper" to get this source:
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps. Thanks for asking.