Hold the control (ctrl) button and then tap the windows button (above the number 6, box with two lines to the right)
Open the shared google drive folder you want to upload to
Click here to find the link to your school's MInecraft google drive link.
Click on the '+ New' button at the top left
Click on 'File Upload'
Click on 'My files'
Click on 'Downloads'
Click on the Screenshot
Click 'OPEN' at the bottom