AirDrop for iPhone SE and MacBook Air
First, make sure your Mac is able to use AirDrop. The following Macs are able to use AirDrop:

MacBook Pro (Late 2008) or later, excluding the MacBook Pro (17-inch, Late 2008)
MacBook Air (Late 2010) or later
MacBook (Late 2008) or later, excluding the white MacBook (Late 2008)
iMac (Early 2009) or later
Mac Mini (Mid 2010) or later
Mac Pro (Early 2009 with AirPort Extreme card, or Mid 2010)

However, AirDropping files between iOS devices and Macs requires a 2012 model Mac or later.



If your Mac does work with AirDrop and AirDrop still doesn't work, here are several fixes:


Reactivate Airdrop (on iPhone)


Go to Control Center on your iPhone (accomplished by swiping up from the bottom of your screen).
Disable Airdrop and then enable it again. Make sure your phone is discoverable to all devices.
Make sure Wi-Fi and Bluetooth are enabled. If it still doesn't work, try toggling the Bluetooth and Wi-Fi button.


Restart your iPhone and Mac


Restart your iPhone by pressing and holding the power button and home button at the same time.
And you probably know how to restart your Mac.


Reset Wi-Fi
Let both your Mac and iPhone forget your Wi-Fi network and/or password and reconnect to your Wi-Fi
Confirm AirDrop is enabled


Go to Finder and click on AirDrop in the sidebar.


Update


Update both your Mac and iPhone to the newest version of OS X and iOS, respectively.


Searching for older Macs?


Make sure your Mac isn't searching for older Macs. Go to the AirDrop page in Finder and make sure it's searching for newer devices (including the iPhone).


Confirm Bluetooth and Wi-Fi are enabled on the Mac


Turn on Bluetooth and Wi-Fi on the Mac. People often forget to turn on Bluetooth on their Mac in addition to their iPhone.



Hopefully, these tips will help you!