Is iphoto a cloud service, or does it store your images on your computer?
The easiest way is to have you photos on a web site (like Picasa, to name one free service), and link to it. To do this, first navigate to your photo on the web site, and copy the URL of the image. NOT the web page containing the image, but the image itself. You can get this by right-clicking on the image, and selecting “Copy Link Location” (in Firefox). In IE8, right click the image, select properties, and copy the URL that’s displayed. (If there’s an easier way in IE, I’m sure someone else will chime in.)
Now, back in the forum, in the reply box, position the cursor where you want your image to appear. Look at the row of icons about the Reply box. See the one that looks like a mountain with a moon over it? Click that icon. Delete the text that’s there (
http://), and paste in the URL of the photo. Click OK. Now the URL of your image is inserted in the post, and the image will appear when you post it.
If your image is on your local drive, you can upload it to the forum. Type in your message, then click “Go Advanced.” Down below the reply box, see the button labeled “Manage Attachments.” Click the first “Browse” button. Navigate to your photo, and double click it or select it and click “open.” Repeat with other Browse buttons if you want to upload more than one. Then click “Upload” and “Submit Reply.” Note that an image must be below 19.5 KB to be uploaded.
