Since your iPhone is a jailbroken one, the upgrade needs to happen on the computer connected with iTunes. Firstl of all, backup all the info on the iPhone beforehand. Here are detailed steps:
- Connect your iOS device to your computer using an USB cable. Wait for iTunes to open and connect to your device.
2.Click on device button to the left of the iTunes Store button in the top right corner in iTunes.
3.Click on the “Check for Update” . If the iOS 7.0.4 update is available it will automatically download and update your device to iOS 7.0.4.
4.You will get a popup message informing you the new update is available. Click on Download and Update button.
5.If you get a popup message informing you that iTunes will update your iPhone to iOS 7.0.4 and will verify with Apple. Click on the Update button.
6.It will then show you the release notes for iOS 7. Click on the Next button. Then click on the Agree button for the terms and conditions.
7.iTunes will now download the firmware file (which can take a long time depending on your internet connection as it can be as big as 2.1GB). After downloading the file, it will process it, extract the software, prepare the device for software update, and install the update.
8.Do not disconnect your device until the update has finished. It can take a few minutes. Your device will be updated to iOS 7.0 and reboot once or twice during the process. You will see while Hello screen after it is successfully update. Follow the on-screen instructions to start using the device.