In this case you must check your outside unit (Condenser) make sure is running, if not check for a tripped breaker, if the breaker keeps tripping you might have a bad compressor (Call a Professional).

If the breaker is not tripping and not running is possible that you have a bad Capacitor but if you are not familiar with electricity (Call a Professional)

If the Condenser is Running, check if the coil is clean free of dust, leaves, grass etc. If the Condenser is dirty turn the system off and clean it with water, you can use your water hose. After you cleaned and Everything is running and is not cooling the System is probably low on Freon. In this case you have to call a Professional.