Creating an Account on Instagram
Before you can start using the app, Instagram will ask you to create a free account. All you need is a username and a password. The reason they require you to create an account is because Instagram is not just a photo app. It's also a popular social network.
Instagram as a Social Network
On Instagram, you can follow other users' photo streams as they post them and you can be followed back by those users (or other users) as well. Using the "Profile" icon located on the lower menu of the Instagram screen, you can search for friends by name or find friends that are already connected to you on other social networks like Facebook or Twitter.
When you decide to follow a user, that user's Instagram photos will appear in your feed, which can be found under the "Feed" icon on the lower menu. You can press "Like" on any photo to let someone know that you admire their photography, or you can leave a comment.
When you take photos using the Instagram app, they will always appear in the feeds of the users who are following you. You can browse through the "Explore" tab to find new users to follow and creative photos to look at.