With materials in hand, you can begin construction. Open your 'Crafting Menu' (Tab/I) and navigate to the 'Base Building' tab. Start by placing a 'Foundation' on relatively flat ground. This is the base of your structure. Then, snap 'Walls', 'Doorways', and 'Window Frames' onto the foundation. Add a 'Roof' to complete the basic enclosure. Remember to place a 'Door' in your doorway and secure it with a 'Code Lock' or 'Key Lock' immediately.
Initial structures are often made of wood. You can upgrade these to more durable materials like 'Stone' or 'Metal' by interacting with the placed structure using a 'Hammer' and the required upgrade materials (e.g., 'Stone Piles', 'Metal Plates'). Upgrading increases the health of your base parts, making them more resistant to raids. Consider adding 'Watchtowers', 'Barricades', and 'Spike Traps' for external defense. Inside, place 'Storage Boxes', 'Workbenches', and 'Campfires' for functionality. Regularly repair your base using a 'Hammer' and appropriate materials, as structures degrade over time and from damage.