First and foremost, I suggest that you begin by reading some essay writing guides online. These essay guides are generally viewable for free, and will really help you understand the basics of writing well. Reading a guide to writing essay pieces will be very beneficial for you, above anything else!
Writing a good essay introduction is very easy to learn. Before anything else, you first need a solid topic. You might want to see our entry on good introductions, as well as our entry about writing essays.
Step 1: Choose a Topic
This is very important because your topic will basically be the north star that you will follow. Imagine if the 3 Kings did not have a North Star to follow, then how would they find Jesus Christ!
Step 2: The hook
It is important that your readers get hooked to reading your masterpiece as early as possible. You can use a quote, anecdote, or anything actually to help them become interested in the essay that you are writing. Good introductions grab the readers' attention immediately.
Step 3: Write the first draft
Don't be afraid to commit mistakes! This is only a draft!
Step 4: Finalize
The last step of course is to finalize your introduction. If you followed steps 1 through 3 pretty well, this will be easy to do.
Here are some other helpful links that you might want to consider checking:
Writing The Essay Intro and Conclusion and this video.
Learning how to write a good essay introduction is not that hard as long as you set your mind to doing it. Good luck!