Hi Amol,
You can download the (free) first chapter of the Mastering ArchiMate book (ArchiMate 3.0.1 compatible, at some point in the future I expect to release an upgrade to 3.1). This first chapter explains the entire language and can be used to self-study. It is free (the full book isn’t :-)).
For the rest, the best way to learn ArchiMate is doing and interact with others that do it.
The book contains the explanation and the rest of the book is about patterns for many different situations. But while the book contains patterns that can be used as they are, it is above all meant to learn how to think about creating your own patterns. Using fixed patterns in ArchiMate is very easy. Creating (changing) them is hard. Just like all design work I might add…
Yours,