Had my BA BOSS 260KW GARAGED FOR 3YEARS BATTER WAS FLAT REPLACED BATTERY. HAVE ALL LIGHT'S.ON DASH ECT REMOTE UNLOCKS DOORS ECT BUT CAR WONT TURN OVER TO START

start with the easy first, check the wire to the starter solenoid.

assuming smartshield light is going out try swapping start relay with one of the other relays can you hear relay click when you try to crank if so give starter a Tap with hammer in case brushes etc.have stuck -
does interior light work/fuse ?