How do you attach picutres? I know this seems simple, but I need to know

On the post, see where it says "Add Attachments" (to the right and below the post box), and browse to an image and press "Attach This".

If it's from elsewhere on the web, use BBCode like this:

Code

[img=http://www.google.com/images/nav_logo6.png]

Basically what DTBK said, but there's also a button when you post called "img" that you can press then enter the URL of the picture you want.