It's complicated, but doable.
1. Under the box for your post, click "Go Advanced."
2. A new window will open with the way your post looks right then, signature and all. Under it is a box for editing, with the text you have entered to that point. Scroll down until you see, in "Additional Options," the tab to "Manage Attachments." Click that.
3. Then you will see the new improved simplified picture uploader deal that Mellow must have added in the last 24-48 hours.
4. In it, there are boxes for you to enter links, and next to each of those is a "browse" function.
5. Apparently, you can upload up five pictures at a time.
6. When you have done that, and they all show up as "current attachments," hold your breath and click the "close this window" tab.
7. You will be directed to the "Manage Attachments" tab and will see your link in a grey box.
8. Then scroll down and click "Submit Reply."
9. Then your post will be posted, and you can gaze in wonder (as I just did) at the magnificence of your computer skills.
Probably a better way to post is the way Igo, for instance, does, where if I understand, he uses an online photo service like Shutterfly or Photobucket, and then inserts links into his posts. We'll have to ask him how he does it later this afternoon when he posts his magnificent pix of the ride he and Falcon are taking to Death Valley.