Since the explanation doesn't really do it justice...
Hacking an ARS:
First, find yourself a happy planet with an ARS on it. Now, build yourself off the Ship Design Hacker in the Econ menu, stuff it in a transport, and drag it along to your new happy ARS planet. Do NOT capture the planet, but you will want to nerf it.
Unload your transport and drop off your ship design hacker. When you click on your hacker with it's 10:00 timer, you'll see something similar to this:
Do not panic, the hacker just isn't done yet. For the next 10 minutes, proceed to abuse the threat that you've unleashed from the AI.
After 10 minutes, you'll see this:
Woo, you've hacked the ARS. Now don't laugh at what I ended up with, but when you're done, your friendly neighborhood ship hacker will have this new 'tab' available, the ARS tab:
Yes, really, I did get a choice between Shield Bearer, Autobomber, and Neinzul Vulture. I'll withold comment, I know some folks really like Vultures. Shield Bearer it is, I guess. *click click click* WHAT?!
You can't PICK one yet, though. You'll notice they're greyed out.
Once you've started construction (you don't even have to finish/capture the ARS) of your command center, these selections will light up and you'll be able to select your ship. My guess is the lack of capture is a bug, but it's not exactly an important one. You've already paid the price for the planet by popping the cmd center, you might as well capture the ARS and get the local K.
Once they're lit, you can click it and you'll get your standard 'new ship' message for MK I/II of your new ship.
Hopefully that'll help any confusion.
Current 'help text' reads as:
This ship is an offshoot of the science line and does not acutally generate knowledge. It takes a significant amount of time and resources to build, but can hack an AI-controlled Advanced Research Station to allow you to (after you capture the ARS, from the ARS tab of the tech menu on that planet) pick from 3 possible new ship types rather than just automaticallly getting one of them. The process requires the hacker to remain stationary on the ARS's planet for 10 minutes while the planet is still under AI Control. This enrages the AI at their planet while the lab is present there as they view this as sabotage, so be prepared for an ongoing AI response against your untis on that planet and nearby.
NOTE: Each time you hack an ARS the AI's response to future hacking increases significantly. Also, each subsequent ship-design-hack will make the problem far worse than the previous one. Beware.
Might I recommend the following rephrase:
This ship is an offshoot of the science line and does not actually generate knowledge. Instead, it can hack an AI-controlled Advanced Research Station that is under AI Control if left stationary on the planet for 10 minutes. Once hacked, a selection of 3 ships will be available upon taking control of the ARS (look for an ARS tab inside the research station) instead of the usually automatically gifted single selection. The AI considers this sabotage and will respond against your units both on that planet and nearby.
NOTE: Each time you hack an ARS the AI's response to any type of future hacking attempt will increase significantly. Also, each subsequent ship-design-hack will increase the response far worse than any previous hack did. Beware.