AirDrop does not transfer over your standard wireless network, so you'll need to ensure that the two devices are physically close to each other. For optimal performance, both devices should be within 30 feet (10 meters) of each other. AirDrop allows for file transfers between iOS devices and OS X computers, but you'll need to meet some basic requirements in order to use it. AirDrop requires:  iOS Devices - iPhone 5 or later, iPad mini, iPad 4th Generation or later, or iPod Touch 5th Generation or later. Must be running iOS 7 or later, iOS 8 if you intend to use AirDrop between your iPhone and Mac. Mac Computers - OS X Yosemite (10.10) or later for transferring between iOS and OS X. MacBooks from mid-2012 or newer and iMacs from late 2012 should work. If your AirDrop visibility is turned off, other devices won't be able to find you.  iOS - Open the Control Center and tap the AirDrop button. Select "Everyone" for maximum compatibility. You'll still need to confirm transfers, so this isn't really a security issue. OS X - Open a Finder window and select the AirDrop option in the left menu. Set "Allow me to be discovered by" to "Everyone." You'll have to manually confirm transfers, so this isn't a security risk. Leave the AirDrop window open while attempting to connect. A common fix for connection problems is toggling your device's Bluetooth adapter off and on again.  iOS - You can quickly do this by swiping up from the bottom of your screen to open the Control Center and then tapping the Bluetooth button. OS X - Click the Bluetooth menu button and turn Bluetooth off and then back on. AirDrop uses a combination of these two connections to setup an AirDrop connection. Check the Control Center on your iOS device and the menu bar on your OS X computer to ensure that both of these services are turned on. AirDrop has always been a bit buggy, and sometimes software updates will fix the issue you're having. Updates for iOS and OS X are free, but they may take a little while to complete.  iOS - Open the Settings app and select "General". Tap "Software Update" and then follow the prompts to install any available updates. This will usually take about 30 minutes. See How to Upgrade iOS for detailed instructions. OS X - Click the Apple menu and select "App Store". Find the latest OS X release, which is usually on the front page of the store. Download the update, which may be rather large, and then follow the prompts to install it. See How to Update to Mac OS X Mavericks for instructions on updating OS X. If you're having difficulties connecting to your Mac computer, try signing out of iCloud on the Mac and then signing back in. Click the Apple menu and select "System Preferences". Select "iCloud" and then click "Sign Out". Sign back in with your Apple ID after the sign out process finishes. If you're running iOS 8.1, there's a potential bug with Apple IDs that can cause connection problems. Open the "iCloud" section of the Settings app. If there are any uppercase characters in your Apple ID, it may be causing the connection problem. Log out and then log back in with the same ID, using all lowercase characters in the email address. This bug was reportedly fixed in iOS 8.2.
Make sure you're close enough. Ensure your devices are compatible. Check your visibility settings. Toggle Bluetooth off and on again. Ensure both Bluetooth and Wi-Fi are enabled. Try updating all devices involved. Try logging out of iCloud and then back in (OS X). Check your Apple ID (iOS 8.1 and earlier).