If you're trying to download and install iOS 8.4 to check out Apple's new music streaming service but your iPhone is telling you you don't have enough space, you might not need to scramble to delete apps and photos.
The secret is iTunes. If you plug your iPhone into iTunes, you won't need as much free space, only about 610 megabytes. This is how people used to update the iPhone in the old days before we could update iOS "over the air," or OTA.
Plug your iPhone into your computer and launch iTunes to get started.