-Edit photos in Lightroom or your favorite photo editing application.
-Export a good quality JPEG from said application.
-Drop picture in a folder on Google Drive called "Instagram Pics"
-On phone or tablet, install an app called "Instasize". This allows you to add black or white bars around an image so you don't have to crop to square.
-From Instasize you can hit the share button and send the photo straight to Instagram.
-I would reccomend never using the Instagram filters over one of these images, not because I hate the look, but because it will change the color of the white bars around the picture and ruin the effect.
-Post. Tag. Enjoy.
You can find examples on my account: @skaliwagify