If you're looking to purchase bitcoin you can use coinbase and bittrex. Those are the two big ones. If you want to open up a wallet. Electrum is a good online wallet. 1august.org is a good site that explains how to set up a wallet and transer any coins that you buy from coinbase or bittrex to your own desktop wallet.
BTC@$4200~i tend to use exchanges: cryptopia and poloniex ccex... Long term it's safer to download the actual coins' software from a legit source and run it on your own system, just in case the exchange goes down. :-D ~may fortune be with youes*