If your image does not follow Instagram image guidelines, you will be prompted to edit the image:
Aspect Ratio - between 0.8 to 1.91
Minimum Resolution - 150 x 150
Maximum Resolution - 1920 x 1080
Maximum file size - 5mb
Editing the Image
Once you click edit, the image resolution will automatically be adjusted to optimal settings.
If it is an aspect ratio issue, you would need to select "Crop" and edit the photo based on the provided aspect ratio requirements.
The image's aspect ratio and resolution will appear on the lower left part of the photo editor screen and will be marked RED if it doesn't meet the minimum requirements.
Once done editing the photo, click Save and you're ready to post!