Silverman wrote:
You can also view your Instagram account on your Laptop or Desktop, you can also send existing images to other friends or Family. Although you will need to have a camera on your Laptop or Desktop to take photos. Any photos taken by your smartphone should appear on your Instagram account on your Desktop or Laptop.
Actually, you can transfer images from your DSLR camera to your phone for posting. All my work, see link below, is from my 5DIII, cropped to 1x1 in LR and then sent to my phone and posted. I've only been in IG since Dec '16 so I'm not sure how the site worked in the past.