1. Backup your device to iCloud or to iTunes
To create a backup with iCloud, simply open the Settings App and tap on iCloud. Then, make sure that iCloud Backup is turned on. Lastly, tap Back Up Now to make sure you have the most recent backup of your data possible. If this is your first time backing up to iCloud, it will take a few hours to perform the backup depending on your internet speed.
You can also backup your device to iTunes. Simply connect your iPhone, iPad, or iPod Touch to your computer and select your device using the devices button in the upper right corner of iTunes. Once your iOS device is connected, tap on Summary and Back Up Now. This will ensure you have a recent backup of all the content on your device.
2. Upgrade to iOS 8
Now that you are sure you have a recent backup, simply click on Check for Update in the Summary section of iTunes and your corresponding device. iTunes will ask if you want to upgrade the device. This is typically the easiest way to do an upgrade because you don’t have to worry about memory constraints on your device.
Alternatively, you can navigate to the Settings App and tap on General –> Software Update. Then, select Update Now. The only issue that sometimes comes up when updating through the Settings App on your iOS device is that you may not have enough memory available. I tried to update my iPad and I got an error message saying that I need 6.9 GB to complete the upgrade. So, if this is the case, simply do the upgrade through iTunes.
Here is something to be careful of as your are setting up iOS 8. After the update, you will be asked if you would like to set up iCloud Drive. Developers are advising against this option at this point until iCloud Drive is available on your Mac computer as well. iCloud Drive will allow you to easily share documents between devices but it requires OS X Yosemite to work on a Mac Computer. If you enable it on your iOS device, then you will not be able to access those shared documents on your computer. Simply tap Not Now when the option comes up and you can easily turn on iCloud Drive in the Settings App when OS X Yosemite is released.
That’s it, enjoy the hundreds of new features in iOS 8.