Click on 'Challenges' in the menu top of the page.
Click on the challenge you want from the ones displayed. If you haven't yet joined click on the Join Now above the owners name. After you have joined a tab called 'Download your page' pops up on the right above the pages already entered. Click on this - it takes you to all your pages on your home page. Under the page you want to enter, click in the box. This places your page in the challenge. That's it. I hope this was some help any further problems please contact me. Joce xx