How did this happen? I want this so much!

http://imgur.com/rUB5bvU

It's not that hard.

1) From what I can see, he has used an existing concrete wall, then added metal roofs and pillars to make a "garage" setup. Easy and cheap to do with any workshop.

2) Build Power Armor stations. These are expensive, but far enough into the game, you will have more than enough to build as many as you want.

3) Acquire enough Power Armors. From what I can see, this guy has a couple of T60s, one Raider Power Armor, a T51 and a couple of T45. He lacks the X-01. If you want to acquire armors, just explore the Commonwealth. Look for military checkpoints, they usually have a Power Armor standing around for you.

4) Remember to remove the fusion core from your parked armor. If you leave it in, then someone will steal your armor.

Yeah, I've already got my workshop built at the Red Rocket ready to make five armour bays. It'll look good once I've found all the frames and pieces.

Never seen a concrete wall like that, unfortunately.

Its not a concrete wall it is one of the Steel ones there are holes in the same place on each panel

It looks like he set them up in the street in front of the Sanctuary Workshop house

In terms of finding armor also look for wrecked military convoys and trains

I have 6 frames so far, plus a bunch of extra parts but I am short of legs. For some reason the sets I find have helmet, torso and arms but no legs.

I am planning on putting a set at each major settlement with a fast travel map right next to it so when i have to help defend a settlement I can fast travel in, suit up and do work.