Wiring spotlights to only come on with Main Beam

[brassmonkey001]

Hi, I seem to be struggling to get my head round what should be a simple job. Where can I take a 12v feed from to activate the relay?
My 2nd gen has spotlights on the A bar but they aren't wired up so I thought I'd get them working. On the wiring behind the headlight plugs are a couple of scotchlocks and

[jim7564]

have spots on mine wired through a relay,luckily the previous owner left the wire needed from the full beam,but i would think its the power you on the connector when on main beam,not sure but i think its a twin filament bulb so one would go off and the higher bulb comes on,sidelights are a seperate light and