How to learn it depends on how deeply you want to understand it. Whether you just want to be able to solve standard problems, or whether you want to understand the foundations of the material too.
Probably the easiest beginners book, no theory at all, is Calculus made Easy, by Silvanus P. Thompson, been around almost 100 years. Keywords: "what one fool can do, another can".
A step up, but still very intuitive and well motivated, is Lectures on freshman calculus, by Cruse and Granberg, unfortunately out of print and hard to find.
For a more standard text, bigger and heavier, with pretty clear explanations, and lots of problems, choose one of the typical college calc texts, like Cooke and Finney (preferably an older edition like 9th), Stewart (same recommendation, say 2nd ed.), or Edwards and Penney (same again, 1st, 2nd, or 3rd ed.).
If you really want a text that explains deeply what the ideas behind calculus are, you need something better, and harder, like Courant and John, or Spivak, or Apostol.
These are no - nonsense, mathematicians version of the material, for the brightest most motivated students, such as top Univ of Chicago freshmen.
Suggestion: go to a college library and sit in the stacks and read until you find one you like.
You can probably check a copy out from a local library. You might also be able to call your teacher or principal and see if they'd be willing to give you a book a bit earlier than usual.
