Hi,
Try this: Click Post New Topic in the area you want to post. Write your post, then at the bottom of the page, put a check mark in "Attach files to this post", then click to post the topic. That should bring up a box to add the attachments, which would be files on your computer. Browse and select the images you want to load from your computer, then upload them. JPG works fine, size should be maybe 600 pixels wide. Where it asks for a URL, there should also be an option to find the file on your computer. You are adding the attachments after you have made the post. Works fine for me, check some of my posts.
I hope this is helpful.
Bruce