You can access the main configuration page for SP Comments by navigating to Administrator -> Extensions -> Plugin Manager -> Content - SP Comments. The Main tab of this page gives you the ability to set all available options.

Comment System: Choose which platform you wish to use for commenting. You can use only one system per whole site.

Show Comment Count: Show the number of comments per article.

Categories Selections: Chose which article categories and/or K2 categories you wish to load & use comments for.