Loam, a soil type considered by many to be the optimal garden soil, is composed of 45 percent sand, 25 percent silt, 25 percent clay, and 5 percent organic matter.
Clay is composed of the tiniest of soil particles. Sand and silt are larger soil particles. If you're starting with 100% clay, and want to make it into loam, then it's a task that most people will not attempt. You're talking about adding silt, sand and organic material to make it usable, and being able to mix it adequately.
Adding organic material doesn't help much as you haven't changed the soil type. And once that organic material (humus) is gone, it's just clay again.
You could try adding the clay to a sandy soil if that's what you have, but it's hard work getting the two to mix well enough.