It's pretty easy. This reply, along with the screenshots, were done entirely with an iPad.
1. Take a photo with your iPad.
2. Create a new post in the "Poker Chip Pr0n" forum.
3. In the "Post New Thread" window, click the "Insert Image" tool (second row of toolbars, fourth toolbar from the left, fourth tool on the toolbar (screenshot below, with the "Insert Image" tool circled in red).
4. In the "Insert Image" dialog box, click the "From Computer" tab (screenshot below).
5. On the "From Computer" tab, click the "Choose File" button. On the resulting pop-up menu from your iPad, click the "Choose Existing" command.
6. Browse through your iPad "Camera Roll" and tap the desired photo to choose it.
7. Back on the "From Computer" tab, click the "Upload File(s)" link (immediately below the "Choose File" button). You'll see some "ATTACH" tags appear in the text of your post. You can click the "Preview Post" button on the lower right corner of the "Post New Thread" window to see how your photo(s) and text look before submitting the post.