To start, you'll need to use a web browser on your PC, such as Google Chrome or Mozilla Firefox, and navigate to the Instagram website. From there, you can use the developer tools to switch to the mobile version of the site. This is done by pressing F12, then clicking on the "Toggle device toolbar" button, and finally selecting a mobile device from the list.
This process allows you to view Instagram in a mobile format, complete with touch-friendly buttons and a layout that's similar to what you'd see on your smartphone. You can then use the site just like you would on your phone, complete with features like scrolling through your feed, viewing stories, and even posting updates.