To schedule a showing in the MLS you simply click the calendar icon while in a listing to send the agent and email request.

When clicking on the listing member, more options will become available, including Contact Agent, Schedule a Showing, or leave showing or open house feedback.

For this feature to function properly, be sure that you have the correct email address in your profile. You may also want to test this feature on one of your own listings so you can make sure these requests will not go into your spam or junk folders.