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 Habitat Builder, you need to scan a fragment of Habitat Builder to craft a new one. You can find five fragments, but you only need to find one.
The easiest to access is not far from your Drop Pod, your base of operations in the early game. The fragment is approximately 295+ meters, south-southeast of the Drop Pod, and a depth of 120+m. It is recommended to have the rebreather, because it will cancel the oxygen consumption below 100 m.
Related: Subnautica: Below Zero Vehicles Guide
The exact coordinates if you want to use console commands or follow the coordinates yourself are: -245-122-250
To easily know how far you are from the Drop Pod, if you look back at it, the distance you are away from it will appear.
Where the fragment is stored, rough sharks roam, which are aggressive, so patiently wait for your moment to head into the depths to locate it. Just look for capsules, and you will find them easily due to the clarity of the water.
There are many more commands, you can check them out on our Subnautica: Sub-Zero Commands List page!