This will appear in Go To... Comet. However, be warned: it's
currently down at mag 22.3, so unless you have set the limiting
magnitude for comets to be fainter than this, you won't see it.
(Or you can set comets to be 'on', in which case you'll see
absolutely everything listed. Or you can set the date to, say,
2006 May 10; on that day, 73P will break mag 6. Or you can
use Tables... Current Comets, and enter a limiting magnitude
of 23. Tables... Current Comets gives exactly the same results
as Go To... Comet, except that you can specify the magnitude
limit for the Tables version.)

A couple of tips:

If you have Guide show all comets down to mag 23, it'll be
a long list. (I just tried it, and got 231 comets brighter than
mag 23.) But you can just type "73p" and it will find that object.

Normally, I would suggest using the Extras... Add MPC Comet/
Asteroid option to get current elements for this object. But
MPC only gives data for "currently observable comets", and this
guy is not particularly currently observable. Still, it's a
good idea to make use of this option from time to time.

-- Bill