Have a problem with colonists that starving and dying? Read the workaround for this issue.
How to Workaround the Colonist Starving Bug
In shorts
To give them food you need refrigerator filled with food and a dinning table.
In details
So you must build a refrigerator, and you must build a dining table of some type. Then you must set your dining tables priority to high.
Otherwise it seems they’ll slowly work themselves to death, or eat infrequently enough that their health takes repeated hits, and they’ll eventually die. Or simply not eat at all.
This is probably a bug at the moment. Particularly given the tutorial makes zero mention of a fridge or a table.
Fridges are under storage, by the way. You may have to scroll to the right to even see them.
Important note
Refrigerators are also hidden in a research for a machine research so until you get the correct prior researches done which I believe is 3 levels down before you can find it.