You're going to see how the Baron behaves in two configurations: with a forward CG and with a rearward CG. The flight starts with the Baron at the hold-short position on the runway.
Your first flight is with a forward CG, so choose Aircraft > Fuel and Payload, and set the following conditions: Fuel: 25 gallons each tank (50 gallons total-300 pounds) Station 1: Your personal weight, plus 10 pounds of flight equipment such as charts, headset, and so on.
Try the procedure again, this time with a rear CG: Fuel: 25 gallons each tank (50 gallons total-300 pounds) Station 1: Your personal weight, plus 10 pounds of flight equipment Stations 2-4: Nothing Stations 5 and 6: 300 pounds of sandbags in each seat Station 7: 300 pounds of sandbags in the baggage compartment.
Ref.: West, Jeff Van. Microsoft Flight Simulator X For Pilots: Real World Training. Wiley. Kindle Edition(Location 12333).