Home Sweet Home

This can be done anytime in the game and is a pre-requisite for other outpost-related achievements like Shipping Magnate and Industrialist.

Just head to a plane, land, walk about a bit and open the output menu (LB on a controller) and you'll have the option to establish an outpost.

Note that not all planet types are habitable until/unless you unlock more skills later in the game - but the game will tell you this as you progress and if you can't yet establish an outpost on your chosen planet. Avoid planets with extreme conditions...