When adding or editing your listing in your MLS service, there should be an option to enable showings on your listing. You can leave this set as "No" which will allow you to use other scheduling services, or "Yes" to enable Showing Suite scheduling for your listings. Once you enable scheduling on a listing in the MLS that listing will automatically appear in your MLS Lite account!
After you enable Showing Suite scheduling on your listing, go to the menu where you manage your listings and select "ShowingSuite Showing Settings". On this page you can set up confirmations for yourself and/or your sellers as well as add any other confirmations or methods of confirmation/notification on the listing.