My first question is how this forum works?
It works like other forums if you have been in any. The advantage of this forum is that it has boards and child boards of discussion. So you discussion accordingly to your interest. There is also local boards, so it is possible that your country's hang out board is here.
What are the don'ts and does here in forum,
They have sent you link to the unofficial rules of the bitcointalk.org, please read it.
also I want to became an Investor what should I do?
If you want to become a bitcoin investor. First learn about bitcoin and second, buy bitcoin. Buy low and hold for long time and sell high
I want to learn more about bitcoin like how to get it.
You can learn more about bitcoin in this forum. How to get it is to buy it with fiat, offer services and get paid in bitcoin, join signature campaign when you are upto member rank and earn in bitcoin