As in you want guided missiles?
Hoo boy.
The basic tl;dr is you need a nasal script that calculates the missile's new heading/lat/lon/speed and moves the model.
The best (in my opinion) way to do this is with guided-missiles.nas as it's currently implemented in the Viggen
(link to file). You'll also need a way to locate the target, either by radar
(here's a really good radar logic file, it's complex though) or if infrared is more your speed, you can see my (admittedly simple) method of obtaining a lock in
this file (mostly the same as the last file, but as I use it in the MiG-21).This is definitely just a high level overview - actually implementing these scripts can be a tad bit of work.
Your best bet is to just do what Lego recommended