Open program called "Paint" Go to "File", "Open", choice screenshot, go again to "File", "Save as", choice any location, but not the primary one, give name to file, set format (.bmp, .jpg, etc etc) and here you go. It will be enough little file to upload it (1,2mb or less) You also can use Total Commander, you will be able to change format in ALL ss at once, but their "weight" won`t change, it will be still 1,8mb