BlkPny:
On the bottom of this page, there's a button (on the right) labeled "Go Advanced." It will open up a new page where you can type a reply, but it will also have a bunch of extra options. One section will be "Your Message" (where I'm typing this now). Below that is "Additional Options."
In that section, click "Manage Attachments." From there you'll have to upload your files in a separate window that opens up. It's a little klugey, but you have to pick the files from the location on your home computer (you can pick more than one), then click the "Upload" button. It will upload the pics, but the window will stay there. From there, you can close the window and be back at the regular page (Again, where you'd be typing the message w/ the "Your Message" and "Additional Options" sections). In the Add. Options section, you pics will now show up (actually, it's the file names of your pics).
Click "Submit Reply" and you should be good. I'm doing the "manage attachments" from memory since I can't open a separate window while writing this right now, so I may have missed a step, but hopefully that gets you in the right direction.