This is something that takes some time to accomplish. You will need good compost before you start. You can purchase compost online or at a local gardening store.
Start by using a pitchfork to break apart bits of the top layer of clay. As you break apart the clay, use a good a mount of compost to fill the broken cracks. Repeat this process throughout the clay soil area. You can also leave a large amount of compost on top of the clay area. You will need to repeat this process each year. Over time the compost will attract worms which will help to further incorporate the compost into the soil. You can also cover the compost with mulch. While the soil will still have high clay content, this is probably good for your area as the clay will hold water better than other sandy soils. The compost and mulch however will improve the quality of the soil. It will get better and better each year.