I would take a wild guess that it means check your coolant!
if it's a new one it is a round plastic bottle drivers side under the bonnet just behind the windscreen washer filler (it's got a a blue cap)
Do not check it when engine is warm, make sure it's cold first! and it needs to be between the min/max marks on the bottle, do not fill it to the top!!
Also bear in mind that IF the level of the coolant is low where has the water gone to ??(if sealed unit) needs to be investigated ias could bring bigger problems in the future, not to scare you just trying to help.IF you are not sure if sealed ask a friend or post further details of car here.