Great question Aji. Asked by many!   Learn. Network. Read. Gain experience. Learn. Attend events. Experiment(safely!). and learn....   

Tripwire have a good intro page. There are many many others... https://www.tripwire.com/state-of-security/7-top-technical-resource-providers-ics-security-professionals

Try the OPSec 210 courses - free - you will know the OT stuff so that helps a lot.  https://www.cisa.gov/ics-training-available-through-cisa

Operational Security (OPSEC) for Control Systems (100W) - 1 hour
Differences in Deployments of ICS (210W-1) – 1.5 hours
Influence of Common IT Components on ICS (210W-2) – 1.5 hours
Common ICS Components (210W-3) – 1.5 hours
Cybersecurity within IT & ICS Domains (210W-4) – 1.5 hours
Cybersecurity Risk (210W-5) – 1.5 hours
Current Trends (Threat) (210W-6) – 1.5 hours
Current Trends (Vulnerabilities) (210W-7) – 1.5 hours
Determining the Impacts of a Cybersecurity Incident (210W-8) – 1.5 hours
Attack Methodologies in IT & ICS (210W-9) – 1.5 hours
Mapping IT Defense-in-Depth Security Solutions to ICS - Part 1 (210W-10) – 1.5 hours
Mapping IT Defense-in-Depth Security Solutions to ICS - Part 2 (210W-11) – 1.5 hours
Industrial Control Systems Cybersecurity Landscape for Managers (FRE2115) - 1 hour

Then there are the ISA and the SANS courses which are amongst the most recognised but not low cost.

There are many other training providers for lower cost - good search will finds them and look through LinkedIn. 

Good luck. There are lots of mentors around to help.  We NEED more OT Cyber people.

Thanks for the reply. Out of the CISA courses, i have done 2-3 of them like 100W, 301V,401V etc. and will do further progress. ISA and SANS are very costly courses which may cost more than 8000 dollars and it is very difficult. perhaps i will do one foundation module of ISA. was looking for some cheaper options. Thanks once again for prompt reply.

Thanks for this info,

Thanks for this info,