Go to the Marriott Hotels home page. Move your cursor to the tab up the top of the page that says "Marriott Rewards". On the drop down menu that appears below the tab select "Use Marriott Reward Points" and you will be sent to the page requested. Just down the page on the left there is a "Travel and Leisure Rewards" section. Click on "Air Mileage" and you will be sent to an instruction page where you can choose your method of transfer. Good luck and happy travels.
One additional tip. If you have enough points to do so, I would recommend that you use your points for the air/hotel travel package. This will allow you to exchange for a combinatio of miles and 5 -7 nights hotel. Point requirements change based on airline miles, and hotel category but this definetly allows you to get more bang for your points. I ahve done this a couple of times and the results have been fantastic!