drain cooling system on 2000 GMC Yukon XL 1500

How to drain the cooling system in a 2000 Yukon with a 5.3 l engine

Asked by for the 2000 GMC Yukon XL 1500
There is a drain cock in the radiator (I think drivers side). There is also a drain plug to allow coolant out of the engine block but my information did not give a location.