It’s a “Pro” only feature.

Version 3 New “Free” and “Pro” Features
– Auto-repost existing and already posted posts based on some rules – one-by-one from old to new, one-by-one from new to old, from specific dates, “older then N days and younger then X days”.
– Add auto-posts to the query that will be posted according to some specified rules (like “two posts per hour”)
– Select what image to use for “Image” and “Attachment” post types if post has several images
– App.net Support
– Custom URL for posts

“Pro” only Features.
– Schedule auto-post for the specific time
– Auto-repost existing random posts from from specific dates or “older then N days and younger then X days”.
– Limit random or one-by-one auto-reposting for specific days of the week and times. (like Monday-Friday from 8AM to 7PM Only)
– Reddit Support