You can repost a previously published post from your Comity dashboard. The repost button will be available under all published posts.
Please note that duplicating the exact same message is generally discouraged, and most social networks have a section in their guidelines or terms of service about what constitutes spam.
If you share the same exact post frequently, your social account may be flagged as a spam account, and your future activity might be blocked by the social network. To avoid this happening, please try to differentiate your post when re-posting and change the message.