System settings is the area where you can define the settings like which page to use for products, which membership module is to be used for your e-commerce module, etc. 

If you have multiple product pages, you can choose which one to keep as default from here -

 You can also choose which membership module should be associated with the e-commerce module by changing this setting - 

 If your site has multiple databases you can configure which one is to be used from here -

 For specific assistance on changing any system settings please feel free to contact support.