Transfering Money From My Bank Account To Bitcoin? Im quite confused about this bitcoin software/system.

I have successfully sync'd to the network (took hours) and have recieved my address. Now, if someone is selling something for 5Bitcoins. What is the process that i have to do to remove money from my Barclays UK account and convert it bitcoins and send it to my wallet.

I really do not understand the process.

Thanks for anyone who can clear up this confusion i have.
If you don't want to deal with the hassle of an exchange you could try our new service for UK users:

https://blockchain.info/wallet/deposit-pingit

The fee is slightly higher at 3.49%