Have a look at the expansion tank. There are 2 marks for low and high. The liquid should be within these 2 marks, close to high level.
Also remember when the coolant gets hot, it will expand. If you fill up to much, it will disappear thru the overflow. Also see owners manual.
Check the whole engine room for marks of coolant, usually the colour (if you use the original coolant) is green. These spots are easy to see. Also remove the black cover from the heater valves and the aux water pump and check the connections. Use a small mirror and look at the bottom of these connections, also under the water pump.