Hey there!
In an introduction, the first thing you want is a hook. You want to draw the reader in so they continue to read more. You can use a quote, a flashback, or whatever you think will make the reader want to read more. Next, you want to outline your main points that you will use for each paragraph. If you;re writing a persuasive essay or an informational essay, you could outline your arguments in this paragraph. Again, you want the reader to continue, so you can make this paragraph just describing in detail what you are going to write, and close it with strong sentences so the reader doesn't get bored. You then use the points you outlined here in the rest of the essay, and use the points and sum everything up in the conclusion.
Hope this helps!