Open the CDU (Shift+7) > MENU > Fuel and Payload (I normally use Page 3/3 and set individual numbers in Business, Coach, Cargo Fwd, Cargo Aft, and Fuel)

Note. Enterring a / (forward slash) before a number between 0 and 100 for Payload, or Fuel, will enter a percentage. Not putting a / before the number will add the Payload/Fuel in thousands (i.e. 10.1 = 10,100lbs/kgs).