You have to have your photos on a web site like Photobucket.com. You cannot upload photos from your computer.
If you use Photobucket.com move your cursor over the photo and a little gear shaped object will appear in the upper right corner. Place your cursor on the "gear" and a dropdown will appear. Click on "Get Links" and then when the new window opens click on "Direct link".
Now go back to the post you want to post the picture to in the UPH site. Click on the box with the little mountain in it above the message area. this will open another box. Right click on the link area and hit paste. This will put the photo link into your message.
It might sound like a lot of steps but once you do it, it's actually quite easy. Hope I have explained this okay. Anyone else can correct me if I've said something wrong here.