No One Knows How to Use This Genius iOS Feature

Ready? First, turn on WiFi and Bluetooth. Then, swipe up on your phone to access the Control Center. Hit "AirDrop," and turn it on by selecting "Contacts Only" or "Everyone," depending on your preference. Choosing "Everyone" means your device is visible to all nearby iOS devices that use AirDrop. To use "Contacts," you must sign into your iCloud account.

Source: Apple