For IPhone 6 and ealier versions: Press and keep the Snooze/Wake and Home buttons simultaneously. Release the buttons when the recovery mode screen shows up with your iPhone. DFU mode (standing for Gadget Firmware Update) on the other hand restores an ‌iPhone‌ if a restart or entering common Recovery Mode https://dcnup.com/how-to-put-iphone-in-recovery-mode/