Selector for page to set up scrolling plugin

I'm trying to set up infinite scrolling for pages on my site, using the Catch plugin. It asks for an item selector. The default is article.status-publish. I'm guessing that if I can figure out what the page selector is, that setting may do the job.

I'm not familiar with CSS, have tried some reading, but all the guides about finding selectors seem to want much more CSS knowledge than I have. How can I make this simple plugin work?

Thanks

dave