well i would start by digging up the grass, and turning the dirt over, you might want to rent a rototiller if it feels like too much hard labor. pull out the rocks. maybe buy some good soil if you’re not sure about the quality of your soil, and some fertilizer or manure to mix in. then start planting! i’m definitely no expert, i pretty much learn by doing and i recommend the same. now is the right time to start planting, especially if you’re wanting to grow stuff from seed. check out organicgardening.com for more info.