While in-game, take a screenshot. After that either while in-game or not, go to your Dashboard and navigate to your Xbox DVR where all your Captures are kept. Then go to whichever one you want and select Upload to OneDrive. When your Console tells you it successfully uploaded the file, then on your computer, go online to OneDrive and log in, then you can open your Pictures and then Xbox Screenshots folder, and your pictures should be in there, to which you can download them to your Desktop then reupload them to whatever 3rd party Hosting site is, mine being Imgur. Then you can link them here.