Upload & Sell: On
You can upload up to five images per post. By default, it's set up for a single image upload. There's a button called "Add a second upload" just under the controls for the caption font & etc., and just above the "Receive email notification" checkbox. You get "Add a third", "Add a fourth", ... as you activate the prior buttons. If you want more than five, just make a second post.
You should be able to Edit your original post, and add four more image uploads.