Hi Mtlman - It can be confusing and frustrating until you get onto it. Each pic has to be "hosted" on a website separate from British Car Forum (BCF for short). When you know where it is hosted, you simply select the "Enter an Image" icon from the list above the text typing box. Next step is to copy and paste the location into the popup box and voila - your pic will appear on the posting.
How do you get a pic hosted on the web? Easy - there are a number of free hosting sites - Flickr or Plaxo are just 2. Type "photo hosting" into Google - I am sure bunches more will pop up. You have to "upload" your picture from your computer to the hosting site - see the specif hosting site's instructions for this - usually very straight forward.
But, how do know the "address" of the pic once you upload it? Simple - right click on the pic within the hosting sight and click on "properties"- the pictures "address" or URL will appear. Copy and paste the address into the pop-up box in BCF as you create your posting, and away you go. Work in 2 windows jumping back and forth.
You can also see where a pic is "hosted" that has already been posted. For example, I went to current posting that has a pic in it . The posting is called called "A Work in Progress" - right click on the pic - and bingo - anther pop-up appears and it contains the address where this particular pic is hosted. (in this example Flickr is the site). See the circled portion below....
Hope this helps - let me know how you make out. Oh... and....welcome to the board. The info here is awesome.