Measure and mark the boards to the desired length. Typically, raised beds are 4-by-8 8 feet. But cut them to the size that best fits your garden space.
Cut the boards with an electric table saw or hack saw.
Stand a long board and a short board on their sides, with ends joined. Screw a deck screw into the top and bottom of the boards, securing the boards together.
Screw the remaining boards together securely so they form a box.
Move the raised bed to the desired location, preferably a flat, sunny location in the garden close to a water source.
Fill the box with soil. Although you will remove some of the older plants annually, you won't have another chance to thoroughly improve the soil. Use a good quality garden mix from a nursery or landscaping firm, amended with plenty of organic material, such as compost and manure.