iPhone 5s IOS update problems
Every update also shows how much space is needed. It will also check that for you when you try to update and let you know.

If you have some free space, but not enough to update over the air, you can either update using iTunes or delete content manually from your device. Whether you use iTunes or update over the air, you'll have the same amount of free space on your device after you update.

Before you start make sure you know your AppleID and password.