As a Graphic Designer and Website Designer, I'm on my computer more than my phone. So, I just learned how to post to Instagram from a Mac (because I like having a full keyboard and my full image library at my disposal!)
Original directions from:
1. In Chrome, turn on Developer Tools under View > Developer > Developer Tools
2. Click on the Toggle Device Bar:
3. Choose a device. Then make sure to refresh/reload your browser window for the interactive icons to appear (+ images, commenting, etc):
Nice! Thanks Google!
To see it in action, here's a Video Tutorial on how to post to Instagram from a mac laptop: