New Blue, no idea how to post vids. Help!

I see I can post video when I create a thread but I wanted to post links to vids guys have posted here and don't see an option on threads I haven't created.
Any help would be greatly appreciated

Find your desired youtube video.  To the right of the "like"/"dislike" hand icons, there is a button reading "about," and a button reading "share."  Click the button reading "share."  This will bring up a few more buttons underneath your "share" button, click the one reading "embed."  This will bring up some text underneath your "embed" button, copy this text.  Now go to make a post, and select "video" for type of post (this option is above the body of your text), then paste the text you copied from underneath the "embed" button.   You can then, if you like, write something underneath this.  When you make your post, the embedded video will be visible and playable.

how do I post gifs?