You have to push the button that says 'Download', and then right click on the image after the image pops up on a different tab. Go to Save as, and then put it in a folder that you would like it in, or just save it as it is. You can rename it, to make it an easier search, and then go to the file that you saved the animated image in. After all of this, go to your deviantart thing, click on your picture, and then 'upload file/image'. You should know what to do after that.