ok, have another look under, the castor rod is the blue arm here:
ur stock arm wont be as flashy obviously, urs will be dark and will have a big bush like the whiteline ones, instead of the rose joing up there^^
now if i can see right, uve got an adjustable bush, that tube in the middle looks like it has an offset hole, this is what gives u adjustment, but it isnt on car adjustment.
so what u need to do is take ur stock arm out, u may need a bit of leverage on the wheel back or forth to free (uncapture) the rod. its piss easy, ull see what i mean when u get under there. then take the arm off to a mechanic with a press, get them to change the bushes over. then before u put the arms back in, move the offsetted hole around to a point where it effectively SHORTENS the arm. this will give u more castor, which u usually want.
then just put the arms back in, will probably need to leverage the wheel again.