Yes, Bob, as Jan said, you'll see the form for the Challenge here:
Click on the "Submit Entry" link in the column on the left, and that will take you to the submission page.
You access the submission page from that page each week, but here's a direct link to the submission page (it will ask you to log in first):
Type your entry in Word, save it as a plain text file just to make sure all formatting has been removed, then you can either upload it via that submission page, or you can paste it from the plain text file straight into the submission box on the Submission page.
One thing we don't recommend is writing it for the first time in the submission box (and not saving a copy to your own files). That has led to many a heartache in the past.
So type it in Word (or wherever), save as a plain text file to hopefully avoid any formatting glitches, then either upload it or copy and paste it into the submission page.
Make sure you don't include your name or any other personal details in the submission box, as the entry will automatically be associated with your account (you have to log in to submit it) and entries have to be anonymous while the judges are reading and rating.
Also, when you choose your level of entry, make sure you click outside the level selection box before scrolling down to the submission box. Many a beginner has found themselves in Level 4 because they scrolled down without clicking outside the box.
Have fun, and if you still have any queries, just ask.