Clear the ground of growth and remove as many weed roots as you can. Edge the area to contain the gravel. Level and compact, cover with a membrane to suppress weeds, top with at least 4"inches of your chosen gravel etc which comes in various sizes such as 1/2" gravel. Rake over and hose down. If you want to make patterns make this by putting edging boxes in the area and fill them with different colours or types of stone.