Thanks for writing. The best thing you can do for any type of soil is add organic matter, such as compost. The compost, as it breaks down, will help push those sticky little clay particles apart so water drains better and your plant roots can breathe. It also adds nutrients to the soil and encourages beneficial microorganisms that help your plants.
I used to live in a house with terrible clay soil... I would add an inch or two of compost every spring and fall to my planting areas and had good success with that.
---Justin, Senior Garden Editor, BHG.com