How do I feed the locals?
I only played for a few minutes, but I was able to feed Carbon to the critters on my planet, Dickbuttia, by simply walking up to them and pressing 'square' when prompted.
On PC: If you can get close enough to fauna without them running away, you get a blue HUD overlay prompting you to press and hold 'E' - this effectively initiates offering food to the animal. Once successful, you will then be presented with a white prompt to actually feed it, assuming you have the materials the animal eats, again by pressing and holding 'E'. From what I gather, this translates to the square button on the PS4 version.
I have had to chase after some animals while holding down 'E' the first time, which has proven effective on skittish fauna. Once the first 'E' is complete, they stop running and the second 'E' has been much easier.