Hi Vicky ,
Congrats on your new career path .
As you already have 3 years of experience in SAP ABAP , I don't think that learning SAP BI will be any
difficult task for you.
After getting the SAP Technical knowledge you can easily learn SAP BI .
SAP BI is all about reporting .
Even there are lots of videos in youtube.com to learn any topics .
There are many documents, articles, and blogs posted by many people on various topics. You just have to use the proper keyword and keep searching for the materials that you find useful and easy to comprehend in the beginning.
Thanks & Regards
Sanjeev Singh