i changed my water pump but how do i flush and fill the radiator and engine? there doesent seem to be a drain cock on the radiator. this is on my 1991 blazer 4.3 ltr

Flish it out a heater hose.
To drain remove lower rad hose.
To fill add 2 gal of pure coolant.
If engine does not take full 2 gallon of pure coolant add about a half gallon to coolant tank.