Filling and checking radiator water/coolant _ Nissan Vanette
 

I just purchased a used 2000 Nissan Vanette.

I am seeing 3 possible points of refilling the radiator coolant/water and/or checking the coolant level:

1. there is a cap on the radiator itself
2. there is a plastic cylindrical bottle with a cap similar to the one on the radiator (this is normally empty).
3. a square plastic container with a yellow plastic cap with the inscription "COOLANT" on the cap. This also has a MIN and a MAX indicator marks on it.

Please my questions are:
1. From which of these 3 points should I fill the radiator with the water/coolant.
2. From which of these 3 points should I check if the water level in the radiator is okay ?

I would very much appreciate and answer, please.