A good beef tenderloin is best lightly seasoned, then seared in a pan to seal in juices, and roasted in a 350 degree oven until the desired doneness is reached. If you don't already have one, get one of those digital probe thermometers, definately worth the ~$25 you'll spend.

You can freeze what you don't use, wrap it in foil, then place the foiled up meat into a ziplock bag. The combination will prevent freezer burn to the meat. Also get as much air out of the bag as you can.