Turn the ANTI SKID SPOILER BK switch to BOTH before takeoff.
http://www.heatblur.se/F-14Manual/cockpit.html#lvc
7. ANTI SKID SPOILER BK switch
Selection switch determining operation anti-skid and spoiler brake systems.
BOTH - Enables both anti-skid and spoiler brake function with weight on wheels.
OFF - Turns off both systems.
SPOILER BK - Spoiler brake, enables spoiler brake function with weight on wheels.