Texas,
What I can tell you so far...
In simple terms:
When you enter Land or Sea modes, the system gives you a "Gun Director" (the Yellow Grid). It is compensating for your ownship travel and showing you where the rounds are going to hit for a given range. Said differently, it is showing you the projected, vector-corrected, sightline to the impact point you have selected to incorporate your ship's direction of travel on the rounds.
Attempt to put the bottom of the Gun Director at the range of your target (For ships, I use the waterline). I've noticed that your graphics card and a bunch of computer-geek 3D rendering effects seems to make this a tad sketchy, and some people seem to be able to see these things more clearly than others, but do your best.
For a SEA target (other boats): You change the range (long/short) and azimuth and try to figure out where your target is going to be one 'Time of Flight' from when you pull the trigger (means to pull some lead). Aim there, squeeze, sip your beverage, and wait for the impacts -- adjust next shot.
NOTE: IF you get a hit, DON'T change anything until you've had a chance to read out the currently displayed range to your fellow gunners (That's how they know the range)...Also, (I think obviously) if you are shooting at a boat, both you and it are moving, so you will have to adjust your next shot to compensate for those motions.
I'm sure there are lots of techniques out there, but this should get you started.
Good hunting!
-Rodent57