How do I change preloaded slider?

I am at wits end. I download and even purchased themes that came with sliders but I cannot figure out how to delete or change the slider. One post suggested Appearance>Theme Options/setting, but that is distinctly missing from the five themes I’ve tried to install. Every other aspect of how to use WP is well documented but this one. Not even Google found anything (in the first 15 pages anyway).

Your help would be most appreciated. Please and thank you.