Start a photobucket account or similar. Upload you pics/videos you wish to share. On photo bucket you have a few sharing options. Generally I click "direct link" and it automatically copies the correct url for you. Then on the CJA message toolbar, click the bottom second from the left icon above the smilies so you get this: "[img ][/ img]"
Then click in between and press CTRL on your keyboard, and while holding CTRL press the letter "V":
[img ]your link will be here[/ img] You aren't really able to attach media like you might do in an email.