If you want to put a picture as a signature go to:
User control panel -> Profile -> Edit signature -> Img and put your link of the pic between
Now, the link of the pic:
If your pic is already somewhere on the internet uploaded, right click on it and click on Copy image URL, and then paste between
If you have it on your computer, you have to uploaded on a website like flickr, imageshack etc. I use http://imageshack.us/, you dont have to make an account to upload a pic there. And after you uploaded, click on the pic first, then right click on it and click on Copy image URL, and then paste between
If you just want to post a pic, but not as a signature,
just go in your post and press Img and again, put the link of the pic there.

and for imageshack:

Also, if you want to post a video from youtube, , go to the youtube box and post the link there.
Make sure the link is like this: http://www.youtube.com/watch?v=Ri7-vnrJD3k&ob=av2n
and not like this http://www.youtube.com/watch?v=NAc83CF8 ... ure=relmfu
If it is like the last one, remove all the things that are after the "&" (Kendra taught me this :) ), like this http://www.youtube.com/watch?v=NAc83CF8Ejk
This goes for every link. So no matter how you're link looks like, in order for it to appear here, just remove all the things after &.
This is how a wrong link looks like
[youtube]http://www.youtube.com/watch?v=rYEDA3JcQqw&feature=relmfu[/youtube]
and this is how a good link looks like




