The other guy was right. It doesn't auto post. You schedule posts, when it's time to post it gives you a notification and loads up the post in Instagram. Instagram does not allow third party apps to post.
With that being said there are a few sites that will actually post for you, but I wouldn't trust them with any of my actual stat accounts. An example is
https://onlypult.com/
I personally just use latergram and post manually a few times a day. It is not fully auto, but is easier than having to go searching for picture and caption each time I need to post.