To post a picture in a thread there a few things you need to know.
1. The picture needs to be uploaded to a file hosting website. I recommend using imgur or photobucket.
2. When you have the direct link from your uploaded image you need to click on this button It will bring up a box asking you for the link to your uploaded picture. Paste the link into the box and click ok.
The button adds image tags to the the link so it looks like this [IMG] uploaded picture link [/IMG].
To post a video:
1. Use the youtube BB Code tags
2. In between these two tags, you have to post the link of the youtube video BUT you don't have to post the entire link. Here's what I mean:
The above is the youtube link you would see if you cut and pasted from your browser.
The bb code on our site wants just the last part of the link after the equal sign (in the above example, it would be BkeAzqhlkNk).
So you'd want to put the following in your post (I intentionally mis-spelled YouTube in order to provide an example, for your post, spell "youtube" correctly)-->[youutube]BkeAzqhlkNk[/youutube]
This is what it looks like if I spell youtube correctly w/the above video reference: