Whenever a showing request goes out in your area you will be notified via text message or through push notifications if you install the app, which you can do here. The notifications will take you to the showing information page. That page will tell you the date, time, location, number of homes to be shown, and payment being offered. You can accept, decline, or counter the showing.
Showings are picked up on a first come first serve basis, so the faster you pick up/accept showings, the better.