Welcome, Debbie! You've just asked one of the "most frequently asked questions"

, so don't feel bad. I was looking for one of the forum threads with Doug's answer to that question (Doug Nelson) is the website creator/host/janitor), but we've hidden that from you also...
If you've found the Challenge that you want to participate in, then it's easy to find the original image -- but it depends on which SET of Challenges you want to work on. If you want to work on an early Challenge (#1 thru some other low number), then click on the page link below, go to the category you wish to try (Restoration - Retouch - Manipulation, etc.) and click on the link on the right hand side of the page where it says "Challenges #1-36 or #1-#19, etc.". The next page will list all the early challenges and when you click on one, the next page will contain a description of the challenge AND the original image -- usually you will need to click on the image to get to the full size version of the image to use. BTW, links are sometimes hard for newbies to see -- they blend in with the overall decor -- usually grey or black.
If you choose one of the more recent Challenges, you will click on the page below, then click on the left side of the page under the category you want -- on the next screen (open up another window in your browser -- this may take a bit of reading from my instructions while you're looking at the other screen

) - Go down about halfway on the page, and look for the page numbers. If there is only one page, the original image for you to work on will be the LAST image; if there are additional pages, go to the LAST page listed, and you will find the original image listed LAST on that page -- in the middle, usually. This will be changed and made easier when Doug gets some new website software programmed to work the way he wants it, but until then -- we just learn where to find stuff.
Any other questions, just ask -- you'll find that everyone here is ready to help -- because we've all had to ask questions too!
Main Challenge Listing Page