where to open demate account and what is its opening amount?

Hello, ram099 ! First you should choose a better company who offers the facility of demat account. There's many company which offer this facility like reliance, religare, motilal oswal, edelweiss etc. or you can also open your demat account in a bank which offer this facility. Generally you can open with a normal amount some company open demat account in free and some charges normally. It depends to you that how much money you want to spend in share marketing. Now, let me describe that what is demat account ?

"It's just an account to store you share in dematerialized form."

I also want to know about the whole procedure in opening a demat account

I am using unicondirect and fully satisfy with their services. They provides dedicated customer services and has a good trading software. they provide lowest brokrage deals also.