The Armor unit in Darwinia is first made available after activating the construction yard, after powering both the mine and the generator. These 3 facilities together provide the raw materials, power, and manufacturing capability to produce the Armor unit for use by the Darwinian army. During the level you will be limited to the Armor units coming off the production lines. After finishing the yard level you will be granted to spawn Armor as an executable program, however only nearby a controlled Trunk Port.
Armor serve a dual purpose, first being an armored transport for the Darwinians, that can load up to 10 Darwinians and deploy them in a different location. The units ability to traverse any terrain, similar to the engineer although at much faster speeds, allows you to place Darwinians just about anywhere. Right click the Armor itself to trigger its load command, and nearby Darwinians will automatically get on board until it is filled.
Second, and most useful, the Armor can deploy into a stationary turret capable of being manned by up to 4 Darwinians, on just about any small patch of flat land. Right click on the area you want the Armor to set up at, and it will speed over and deploy instantly. In addition, you can bring Darwinians to man the turret when it deploys, and it will jettison them into the air out its back before turning around and deploying in this case. As soon as the turret is up, the nearby Darwinians will rush over and man it. The speed of the Armor allows it to easily speed right through large virus infestations unscathed. Optionally you can command a manned turret to direct its fire if you find more pressing targets to focus on.
You are not limited to how many Armor you can create, although only so many turrets can deploy in a given area, and while they are still Armor they will take up a program slot. The turret is also the most powerful weapon available to your forces, especially after upgrading its range through research, since it allows the Darwinians to attack and successfully kill all virus types, although a single turret may be overrun by a large force, and they can be destroyed by enemy or friendly grenades.
Lastly it is incredibly important to realize that while your green Darwinians can man these turrets, so can the enemy red Darwinians if they reach one that is unmanned, or overrun one of your own. If this happens, the turret will be turned on your forces, and can really mow down large groups rather quickly. If this happens, one of your best bets is to send several bait Squads to draw the fire, and follow up with one under your control, and either grenade or airstrike it out of existence.
The Armor begins at v1.0, allowing 10 Darwinians to board the unit until it is at full capacity. Researching to v2.0 grants additional range and a max capacity of the transport to 20, v3.0 allows for 30 Darwinians and a very long range, while finally v4.0 grants a capacity of 40, and enough range to mow down viruses from extreme range, which if combined with a great vantage point, means no viruses are getting anywhere near that turret.