Discourse (this forum software) doesn’t support hosting videos, but if you put a link to a video on its own line it should turn it into an embedded video. This feature is called a onebox. This should work for a number of different hosting sites (YouTube, Vimeo, Twitch, Instagram).
As far as where to post it, there are a couple of different threads floating around, like Community video gallery, but the most active one lately is probably the Patch of the Day thread.