There is a sticky at the top of the forum about this subject. I tried following some of the advice but was unsuccessful. With the help of member shovelon I figured it out and thought I would share my process. If this is helpful perhaps the moderators will make it a sticky.

Step 1 - get your picture scaled down to a reasonable size. I recommend no more than 600 or 700 pixels wide. There are MANY programs to do this and I will not go into it here. Google is your friend.

Step 2 - Use the site's "Insert Image" button. It is currently in the second row, 6th from the right. It will ask you to insert an image "From Computer" or "From URL". Choose the Computer tab. Click "Select Files" from the bottom of the dialog and navigate to the file you wish to post. Press OK and then "Upload File(s)".

Step 3 - Observe that you have added to the post something which looks like
[ATT ACH]99999[/ATT ACH]
except that ATT ACH is ATTACH - had to put in the space to keep the web page from processing the code. This will not display your picture. However, it does have the magic number of your picture 99999. Save that number and delete the line from the message.

Step 4 - Insert this code into the message. Again I have added some spaces so you can read the code and not the end result.
[I MG]http://www.millerwelds.com/resources/communities/mboard/attachment.php?attachmentid=99999[/I MG]
"I MG" becomes "IMG". Note that I inserted the image file number from step 3.

Step 5 - Preview the post to make sure it works and that the image looks OK

Here is is in action. I uploaded and image and got the code
[ATT ACH]31806[/ATT ACH]
which produced a link to the file as shown here: defective.jpg

And here is the hand crafted code
[I MG]http://www.millerwelds.com/resources/communities/mboard/attachment.php?attachmentid=31806[/I MG]
and the result:

Hope this helps. Please ask if anything is unclear and I will update the post.

Ken