Hello Arunava,
I'm assuming that you've found DocOps, which has the product documentation. There is a "Getting Started" section in there:
CA Process Automation - CA Process Automation - 04.3.02 - CA Technologies Documentation
This can get pretty deep though in places, for a beginner. It is the key documentation though.
I think that a training course is an excellent way to start, as it grounds you in all of the basics.
The thing with CA Process Automation - like many solutions that are highly configurable - is that you may find that the real learning experience is not with the installation and initial setup. Instead, it is configuration of all of the business cases and converting them into flows. Because you can use a lot of different languages and ways of writing the flows, each site sets things up very differently.
Searching the internet will also throw up guides, such as this search term will have some key lessons in short videos: "ca process automation youtube"
Of course if you get stuck in specific places, this Community is an excellent place to put up short questions.
Thanks, Kyle_R.