Tittle. I never used gifs so i don't know how to make them work in spoilers or an actual reply to a thread. Any help?

These days lots of gifs are in webm format or gifv and they won't work in any way shape or form that I've found. Normal .gif files work the same as normal images in posts. Click the little image icon on the border of the reply window and paste the url. Alternatively just write the actual bbcode markup and stick the url between the tags.