Add Compost and other organic matter to your soil. This is not a once-an-done project. Successful gardening involves a continuous process of enriching the soil and composting organic material. This can be done in a variety of ways: compost piles, compost bins, mulching, kugelkultur, verimiculture, etc.
Often when starting a a new garden, one starts with a bulk delivery of compos tor psil amendment, as well as wood chips. Bringing in more organic matter is fine, but definitely value and use what you already have on-site.
Additional organic matter will benefit sand, loam, or clay-based soils.
You may already know that blueberries (Vaccinium spp) need acidic soil. Often soil with high amounts of organic matter at all stages of decomposition is acidic enough to grow blueberries well. However, if you notice symptoms of nutrient deficiency, you can further acidify the soil with the addition of elemental sulfur, but this is not always necessary.
You might want to invest in a professional soil analysis to give you a baseline of understanding about your soil.