I think only the Area light allows you to adjust samples. You may be able to achieve what you need by adjusting the "softness" setting. Click on the light in the object browser to select it. If you scroll down in the panel in the top right, you will see the "softness" setting in the "Shadow" subsection. I am using the latest official version of Cheetah, 7.4.2. I'm pretty sure in earlier versions each light type had adjustable samples.
Hope this helps.