There's nothing wrong with 600 rpm so long as it's steady and doesn't run rough or sound as if it's going to stall. Was the idle speed higher than this before?
If you car has a throttle cable then the idle (or tick over) speed is usually set by the idle control valve, located in the throttle body. The idle control valve opens to allow air to bypass the throttle butterfly when it,s closed and keeps the engine running. You can remove the idle control valve and clean it as well as clean out the air passage in the throttle body which tends to get carboned up.
If your car doesn't have a throttle cable then the idle speed is set by the ECU and there's not much you can do about it other than take it to a garage.
2015 Antara Exclusiv 2.2 163ps Manual 2WD