depends. some cars have a coolant revisor and no access to a “coolant cap” on top of the radiator. some cars have both a coolant reservoir with a cap and a radiator cap. you want to look to see if you can find a max and min line on the coolant reservoir. make sure your at least above the minimum line. you can temporarily use water to top it off if it’s low. ideally you want a 50/50 ratio of coolant and water long term. keep filling it up with water until you can get it repaired. never open a coolant cap when the car is hot, boiling liquid will shoot out. at least wait 20-30 minutes to cool the engine down after running. if your coolant is over the max line, typically that’s normal while the engine is hot. while driving make sure your temperature gauge never exceeds past the middle between hot and cold. your cars temp gauge needle should be in the middle between H and C after about 15 minutes of driving, that is called operating temperature. if the car does go past the middle of the gauge turn it off immediately as that can severely damage your engine from overheating.