My original answer to a question on Quora can be found here: Is it possible for me to advertise on Instagram?
Yes, one can advertise on Instagram, but not directly (as in, through placing ads like on other websites/apps). A lot of popular Instagram accounts advertise products to their followers directly or indirectly. A valuable practice to follow, if in case you are planning to advertise products and services to your followers, is to announce the Instagram post as an ad/advert to your followers. Followers appreciate this, because they feel you are being honest to them. You can search for agencies that help popular accounts get connected with brands and companies that are looking to advertise on Instagram. You can check out Socialtye (Link here:) and Viral Nation (Link here: ) for more information and to register yourself as an influencer.
P.S. I am not affiliated with Socialyte nor Viral Nation.