The posting process with Instagram is a little different because they don't let outside apps post on your behalf. When you schedule a post to go out, we will send you a notification at the scheduled time so you can complete your post. Tapping on the notification will launch the Ripl app and then you'll see a message asking if you want to complete your post as scheduled, tap "ok" and the Instagram app will launch. Your caption should be copied and pasted so you can complete the post quickly.
If you missed the notification, you can always re-share the post by tapping on the post in your home screen. Tap the pencil/edit icon in the upper right hand corner to open a copy of the design in the "customize" step, tap the ">" to go to the final share screen and select Instagram as your output. Don't forget the final "share" button and after the uploading completes, you'll see "launch Instagram."