Downloaded ios7, but how do I install it? - 1

I downloaded ios7 for my iphone but now when I click "update" it starts downloading ios7 again rather than just installing the one thats already downloaded!

What am I doing wrong or how do I get the fully-downloaded one to install?

Waiting to downloaded it again would take hours.

Note: By downloaded I mean I clicked the "download only"option rather than download and install

Download via iTunes:
f you are near your computer with iTunes, it might be faster to update this way. In my experience, updating my iPad 2 via iTunes was faster than updating my iPhone 4S over the air. The first order of business is to update iTunes to version 11.1. Open iTunes and then click iTunes > Check for Updates to install the latest version.
Once iTunes is up-to-date, connect your iOS device. Click on your device in the upper-right corner of iTunes and then click the Update button.

A pop-up window will appear, alerting you that a new iOS version is available for your device. Click the Download and Update button. (Or, if you are going to need your phone in the near future, opt for the Download Only button to download it now and install later.iOS 7 is a 649MB download for my iPad 2 and took the better part of an hour to download and install via iTunes.)

If you chose to download and install the update, you can monitor its progress in the status window at the top of iTunes. Keep your device connected to your computer until your device restarts. After restarting, your device will greet you in any number of languages by the blinding white iOS 7 setup screen.

Slide to enter iOS 7's setup process, which will have you tap through a handful of screens to configure settings, including Location Services, iCloud, iMessage and FaceTime, Find my iPad, and a passcode.