How do I delete photos or videos I've posted?
To delete a photo or video that you've posted, tap (iPhone and Windows Phone) or(Android) above your post and then tap Delete.
Keep in mind that you can also archive posts to hide them from your profile and make it so your followers and other people on Instagram can't see it. When you archive a post, it keeps all its likes and comments.
It isn't possible right now to delete multiple posts at the same time.