How do I reset the air conditioner?

Hello, there is not "resetting" of the air conditioning system. You'll have to see what is happening to cause the air to not blow cool. The system under the hood could be low in refrigerant charge due to a leak, you could have an electrical concern at the coil on the compressor, the cycle switch or the high pressure cut of switch, or you could have a temperature control issue inside the car. You'll have to have some first hand evaluation performed. Good luck!