Secure boot

Enabling secure boot on Dell Latitude E6440 running Fedora 22

I've wiped the Microsoft OS that came with this machine and installed Fedora. Now, I'd like to enable secure boot.

Boot to bios with F12

It looks like this:

Use the ^(Up) and v(Down) arrow keys to move the pointer to the desired boot device.
Press [Enter] to a attempt the boot or ESC to Cancel. (* = Password Required)

Boot mode is set to: LEGACY; Secure Boot: OFF

LEGACY BOOT:
    USB Storage Device
    CD/DVD/CD-RW Drive
    Internal HDD
    Onboard NIC
OTHER OPTIONS:
    BIOS Setup
    BIOS Flash Update
    Diagnostics
    CHange Boot Mode Settings

The bios indicates that secure boot is off