Don,
suggest you read the HELP ! page (top right). I think you then need to generate a User Profile and check that your name actually shows up on the list of User Profiles page (Profiles - top left); and at this stage your name should be in blue on the page where your posting(s) are indicating that the Forum has your Profile - the blue is a live link to your User Profile .
Go to Post New and you will see the box for your text and beneath the box see

Type in your text; get your cursor at the point where you want an image from your computer uploaded; click Browse; find your pic, click OK or upload or whatever your Apple calls it and wait about 8 seconds then Hey Presto, a long line of code appears starting with uplimg in square brackets, a long temp file name and ends in /uplimg in square brackets.
Go down to the bottom of the page and click on Preview. Wait for your page to show up with pic included.
You can of course put in more than one pic

Note: the pic file in your computer needs to be less than 5000kB, should be about 500 pixels wide or less and in .jpg or .gif format.

Do not make the mistake of using the Image (Alt+P) box - second from the right box on the toolbar below Subject:; it will not work with files on your computer.

God luck with posting.
Cheers from Martin B.
Mandurah, Western Australia.