First of all you need to figure out where and when you want to go. (Isn't it summer already?) You can certainly go on the website for search for location and point levels. Then you need to sit with your co-worker so they can book the vacation using points. This can be done online but I suggest over the phone so that your name will be listed on the reservation as the guest. If you are signed up for Marriott Rewards (it's "free"), make sure your MR number is listed on the reservation. Any charges you incur on the room...room service, excursions, etc will turn into points for you.