Hey satveer, welcome!
Well, for beginners, the most important thing you need to know about testing is:
The art of giving good feedback
Nobody likes being told that they have failed. Give good feedback, and that is feedback that is:
Professional - No swearing, no insults, no “your shit sucks”, or “don’t you have common sense”.
Detailed - If you have already done the work of producing an error in the system, save your engineer the the trouble of guessing and coming back to you to ask you how you produced the error. Document it and tell your engineers how you produced the error - what was the environment (devices/browser/version) and what are the steps you did? Your engineers will thank you for it.
Another thing I really love about good QAs is having a friendly rivalry with them. Makes my day when my QA tells me, “Congrats! I didn’t find a bug in your new feature this round!”. That’s also good feedback.
The second most important trait of being a QA is to be … evil. Be the most rotten user ever, and do every stupid thing you can think of to break the application.