How to downgrade my iphone 5 from iOS-7 to iOS-6?

I bought a second hand iPhone 5 since few days, iOS-7 Beta installed in. This iOS is unstable and does not run prefectly on my iPhone. I'm not a developper, just i would like to downgrade it to iOS-6 stable version. ANYONE CAN Help ME?

Step1: firstly download the latest ios6 firmware according to your iphone model.
step2: connec your iphone5 to the computer and install the ios device drive.
step3: press the home button and the sleep/wake button at the same time to enter the DFU mode. After 10 seconds release them.
step4:Then press the home button till the iTunes pop up a information box which says it detected to the recovery mode and click OK. Then your phone will turn to black screen. After that you can see a prompt and hit on Restore iphone.
step5: next you should choose the downloaded ios6 firmware and open it. When it is required to confirm the restore, click the button of restore.
step6: the process may takes you 10-15 mins, then it will succeed to downgrade to ios6.

Once you've installed iOS 7 once, it's only safe to downgrade if you register your device's UDID with a developer account through a site like http://www.udid.in/.It's $5, and they literally registered my 4S instantly.