How did you try to upload? This should be the method (sorry if I'm teaching my Grandmother to suck eggs) ...
You need the pictures on your computer. Give them a descriptive name (not, for example, what a camera names them ). Log on to the wiki and go to "Upload file" in tool box on the lefthand side of the page.
Click "Browse" and locate the photo on your computer in the new window and double click it. Click "Upload file" and the job's done.
When it's uploaded you will have a screen withyour uploaded photo and above it "File:Your file name.jpg" Use the "File:Your file name.jpg" to put the photo on your page.
From the look of the error message, were you uploading direct from your PC?