Open Instagram and find the image you want to copy
On a computer, right-click the image and select Copy image if available
On a phone, take a screenshot of the image
Crop the screenshot to keep only the image
If the post allows it, use the Share or Save options to keep a copy
If you need the image file, use a browser on desktop and inspect the page source or download the image from the page if permitted
Make sure you have permission to copy and use the image