From the dark inner shore area where you created your seeds you need to make your way to the right. There is a pod there where you can sleep to advance the day, you'll awake in your cabin which exits to your farm on the right. There you can plant your seeds, but you'll need to plow a red whaleskin tilee first by selecting your tool with (2), then holding (LMouse) on a nearby tile. Happy seeding, the next update will prioritize creating a better new player experience to make this all more clear. The game is still very unintuitive in many regards, sry.