The Habitat Builder is what you use to create permanent structures that you can form into a base. The base will be one of your main hubs for creating and storing the majority of your items.
To get the Habitat Builder, you need to scan a fragment of the Habitat Builder to fabricate a new one. There are five fragments you can find, but you only need to find one of them.
The easiest one to get to is not far from your Drop Pod, your base of operations at the start of the game. The fragment is about 295+meters, south-southeast of the Drop Pod, and a depth of 120+m. It's recommended to have the Rebreather, as it will negate oxygen consumption below 100m.
The exact coordinates if you wanted to use console commands or follow the coordinates yourself are: -245 -122 -250
For an easy way to tell how far you are away from the Drop Pod, if you look back at it, the distance of how far you are away from it will appear.
Where the fragment is being stored, Brute Sharks are roaming about, which are aggressive, so wait patiently for your moment to head down into the depths to locate it. Just look for capsules, and you'll find them easily due to the water being clear.
There's a lot more commands, you can check them out on our Subnautica: Below Zero Commands List page!