From what you say, what I would do is put red to permanent live, earth it to the bodywork (I presume it has a ring connector or a metal mounting bolt hole etc for this). Then to test it, put the white wire also to live. It should now go up. When you remove the white wire from the live the aerial should go down.

If it works then you can put the white wire to a wire that comes live when the ignition is turned on, or some headunits have a live output, so aerial is up when raio is on, but not when a cd etc is playing.