you can plant two different things to get food. first palms and second potatos
1. Palms : to plant it you need ; Palm Seeds(get it from barrels) and a Tree Cropplot(8 Wood, 4 Ropes). Just place the Tree Croplot and press interact button("e") with the Palm Seed in your Hand to plant. Wait for the tree to grow and chop it with an Axe(4 Wood, 5 Iron, 1Rope). After chopping you get Coconuts(4<) which you can eat, each coconut will give you 1 Palm Seed after eating.
2. Potatos : for this you need a Cropplot(4 Wood, 2 Ropes) and a potato(from barrel). Place the Cropplot on the floor and press the interact key("e") to plant the potato. When finished growing each planted potato will give you 2 potatos back. You can cook them on a cooking station.