Hi, I’m Chris. Welcome and thanks for asking your question!
While the engine is not running and cool, you need to loosen the drain on the bottom of the radiator facing the engine and drain the coolant. Then you need to gain access to the thermostat housing and remove the complete hosing or top half if you choose to access the thermostat. Step one is to remove the air intake tube, shown below in a Ford download.
Step two is the thermostat and housing
Step 3 is refilling the cooling system which is not done as simple as it would seem, pay close attention to all the steps below.