The cooling liquid has been added before leaving the factory, with high overall sealing and long service life, so there is no need to worry about replenishing the cooling liquid.
As for how to judge the problem of insufficient coolant, it is generally difficult to judge, unless it is transparent, you can directly observe the liquid level, but yours can't.
The arrow should point to the coolant filler. I haven't used yours, so I can only guess.
Normal use, don't worry about the problem of coolant, this filler should be used for maintenance.