Download the vid.
Open up photoshop.
Import video frames to layers.
Select the video.
Choose the section of the video you want to make into a gif (don't select the entire video because it limits you to only 500 frames)
Once you have an approximate span of the video you want to gif...go ahead and delete unnecessary frames.
Click save to web. It'll populate a preview of the gif.
Check to see its file size. You may need to play with the resolution.
When done, save image to your desktop/upload to a site.