Instagram can be used on a computer on Instagram.com. Simply login in or create an account to get started. Instagram's website is a bit different and has fewer features than the Instagram app for ...
You can post on Instagram from your phone or computer, though the process for each device is very different. The Instagram mobile app lets you post photos, videos, and Stories with just a few taps.
Under normal circumstances, Instagram asks you to log in to view posts, especially ones on private accounts. But there are ways to view content without your account, allowing you to remain anonymous.