Log in to your Instagram on Chrome. Then right-click the page and select the Inspect to open Develop mode at the right of your screen. Click the second tablet icon at the top Develop toolbar. Now the left Instagram should look like a mobile. Click the drop-down option on the toolbar at the top left corner and choose a suitable mobile device. Then the Instagram will switch to a mobile version. You can find the + at the bottom of Instagram. Click it to add a photo from your PC. Follow the steps, and you can upload it on Instagram.