On Android, you will see the "Share this photo on PicCollage" reminder after a certain number of photos are taken by the camera. By tapping on this reminder, you will be able to open PicCollage and start to edit the photo directly.
However, if you want to turn it off:
1. You can tap on the "Don't ask me again" in the notification 2. Or, you can turn it off from the app Settings -> Share photo reminder -> switch it OFF