What is a one-sentence summary of the following article?
Since Instagram uploads take place entirely on your mobile device, it is much more convenient to edit the photos that you take directly on your phone. There are multiple apps available that can resize your photos so that Instagram does not crop them. If you want to resize a photo on your computer before uploading it to Instagram, resize it to 612 X 612 pixels. This is the size of the Instagram format. If you want to post big pictures on Instagram that are too large to post normally, this resizing app will help you do that. Depending on the app, the features may change. Most will allow you to resize your image so that it fits, and others will allow you to crop your existing image so that the cropped section fits into Instagram. Open your Instagram app and browse for your newly resized image. Upload as you normally would and you won't lose any part of the image due to cropping.

Summary:
Download an Instagram resizer app. Run the resizer app. Upload the image to Instagram.