Tuning a Diamond NR73B

[Madduck00]

new ham here.
installed the above antenna on my jeep, going to run my FT3D off it.

with a dual band antenna, is one band tuned off the base of the antenna, at the element holder? and the second band at the phase inductor?
or will i work between the upper/lower limits of both bands and tune only at the element holder?

thanks for the help.

cheers...73