Good work. Two drones have been destroyed. If you have been following instructions, they were the two high flying drones (>5,000ft).
Take a moment to check the arcs of your guns and CIWS mounts by selecting your destroyer, bringing up the Weapons dialog (F8) and checking the 'Show Arcs' box next to the entries for 127mm/54 Mk45 Mod 2 and 20mm/85 Mk15 Phalanx Blk 1 CIWS. Note that one gun covers the forward arc, one gun covers the rear, one CIWS covers the starboard bow and the other covers the port quarter.
For targets outside 5nm it is assumed that the crew perform whatever manoeuvres are necessary to 'unmask' your weapons and these arcs are not taken into consideration. Within 5nm, however, weapons are only able to engage targets within their arcs. Your destroyer is designed to have 360 degree coverage from at least one each of its gun and CIWS mounts, however you can bring the most weapons to bear on targets off the port or starboard waist (2 x 127mm guns and 1 x 20mm CIWS). In this training scenario it is best to turn your ship so that it is presenting a broadside to the incoming threat when preparing to engage a target inside 5nm. When responding to air threats in a non-training environment it may be better to turn head-on to the threat to minimise the radar cross section of your ship. By default, the AI will handle manoeuvring for you while you concentrate on other things.
While we have the Weapons dialog open, note that there are three types of ammunition in your magazines for the 127mm guns: HE-CVT, HE-PD and WP--acronyms for High Explosive-Controlled Variable Time, High Explosive-Point Detonating and White Phosphorous respectively. For anti-air engagements, we want HE-CVT which is loaded by default (incoming air threats is not the time to be switching ammo types!). HE-PD is more effective against surface vessels and shore targets, while WP is effective as an incendiary against soft targets.
Unlike the cannons of the age of sail, our ships 127mm guns are rapid firing, accurate, and can be guided by a variety of radars and electro-optical sensors aboard our destroyer. The Phalanx 20mm CIWS is even more capable against air targets, and since it is able to operate autonomously it has no OODA delay: a huge advantage when dealing with sea-skimming anti-ship missiles travelling at Mach 2+! Like the illumination required to direct your SM-2 missiles to their targets, fire-control sensor activation is taken care of automatically by your crew and requires no action from you.
Remember to manoeuvre to unmask both guns if possible. Note the OODA delay present when using missiles and guns: OODA stands for Observe, Orient, Decide and Act and is the time taken for your crew to organise their response to a detected contact. The Phalanx CIWS operate autonomously and therefore ignore the OODA delay, which when combined with their potent anti-air capability make them very effective for missile defence.
The final line of defence are decoys. Our destroyer is equipped with Mk36 SRBOC (super rapid-blooming offboard chaff) launchers that are also able to launch flares, as well as a Nixie towed torpedo decoy. Decoys are automatically deployed by the crew, and in this case all decoys also operate autonomously and therefore ignore the OODA delay. The effect of decoys is determined as part of the Weapon Endgame Calculations. To see these calculations, enable them in the Game > Game Options > Message Log settings and view the message log entries--note that since we are not defending against live missiles in this training exercise, decoys will not be deployed.
Prepare to engage low-flying target drones closing on your ship. Manouevre to expose your weapons, and allocate your guns and CIWS with manual (Shift+F1) or automatic (F1) attacks to destroy them.