How can I reate a block chain and a bitcoin wallet as I want to start trading in bitcoins. I have never opened a bitcoin waller or block chain and am not sure if I should have both?
A blockchain is the basic data structure used to record the transactions in the network. It already exists, you don't need to create it. This is like asking "I want to send an email, how do I create an internet?".
You need Bitcoin wallet software. See https://bitcoin.org/en/getting-started for more information.
Go to blockchain.info. Click on wallet at the top, then click on Create wallet. Fill out and then it will send an email that you will need to confirm. After you login, you'll need to complete security information but it's really self explanatory at this point.
It depends on where you live if you can purchase bitcoin on blockchain or not. If you live in USA, you can't and will need another waller to buy.