Well, there is no way to fill from the radiator. If you have the V8, then your choices are the degas bottle (coolant reservoir) or the engine fill cap. If you have the V6, then you are left with only the degas bottle, AFAIK.
If you only loose a little coolant, just topping it up should be okay. If it's more, then you'll have to do the factory bleed procedure exactly.
Here it is for the V8:
2006 Lincoln LS Workshop Manual
PS: If you are changing the throttle body because of ETC failsafe, you will probably be disappointed.