We should note 1st of all that you can update your iOS device through a Mac with iTunes without having much extra space. That might be the quickest/easiest way to go
Today iOS 8 came out. There was a massive rush to try to install and download it. The one thing that we were not prepared for or made aware of was the need to have up to 4.7-6.9 GB of space available in order to download and install iOS 8. The reason you needed 4.7-6.9 available is that the 1.1-1.3 GB download of iOS 8 also needs to move a lot of files around during installation.
If you are like us, you might not have that much space needed on your iOS device. We’ve spent the last year downloading music, videos and apps to the point where our iPads tell us to stop. So now we need to delete some of our stuff.
Once you free up your space on your device, and back up your device, then you will be officially ready to download iOS 8. In this how-to I will discuss the two different methods to free up storage space off the device, either from the device itself, or managing the device while being connected to the computer through iTunes…
1. Manage storage space through the device. If you are at the screen to update to iOS 8 and you see the error message about needing more storage space you can tap on Usage Settings. If you are not there the other method to get there is to go into Settings. Then tap on General, and then tap on Usage down at the bottom.
Please be aware that the more data that is stored on the device, the longer it takes to load and break down app by app what is taking up the most storage space. This can range from a couple of seconds to a couple of minutes. Once it loads it will then show you all of the apps on the device as well as how much room and data the app is taking up. Some culprits that are notorious for eating up a lot of space are graphic intensive apps/games like Disney Animated, as well as media.
To delete the graphic intensive games/apps, tap on them in the list. Then press the button Delete App in red. You can do this with a lot of your apps. You can always redownload them again for free later by going into the App Store and in the white bar down at the bottom pressing the Purchased button, which is second from the right (on an iPad), or located in the Update button all the way on the right (on an iPhone or iPod Touch).
Media consists of music, video and pictures. If the music and videos are purchased from iTunes you are always able to redownload them for free onto the device. Just like with apps you are able to redownload them by going into the iTunes store and tap on the Purchased button.
To delete Music off the device, tap on the Music button then tap on the word Edit in blue in the upper right hand corner and then press the red minus button next to music. Finally press on the red button Delete on the right hand side. It will delete all of your music.
Deleting Videos is similar to deleting Music. Tap on Videos and it breaks it down and shows you the different TV shows, Movies and Music Videos in there. Tapping on each series will show you which TV shows are downloaded. Pressing on the word Edit in blue in the upper right hand corner, produces red minus buttons next to each episode. Tapping on the minus button will then have you confirm you want to delete the episode delete the episode by pressing on the red button Delete on the right hand side.
Deleting Pictures is tricky because you want to make sure they are backed up. Easy ways to back up the pictures is to back them up to Dropbox or back them up onto your computer. Once you have done that, you can delete your pictures. To delete all of the pictures at once from your device, you actually have to open up the Photos app and manually delete each picture by first tapping on the word Select in blue in the upper right hand corner, the tap on all of the pictures and then tap on the blue garbage can in the upper left hand corner. Finally then you confirm by pressing on Delete 7 Photos in red.
2. Manage storage space through iTunes on the Computer. Connect your device to iTunes on the computer with the USB cable that came with the device. When you click on the device in iTunes, it shows you down at the which type of content takes up the most space: audio, video, photos, apps, books and other. Hovering the cursor over the different colors shows you quantity and size.
If you press on the categories up at the top, Apps, Music, Movies, TV Shows, Books and Photos you are then able to uncheck what is synced and then press apply.
Hope this helps you free up much needed space on your device, so that way you can get iOS 8.