My AC is not blowing very cold. How do i go about charging the system myself ?

Cold A/C is more about removing air and moisture from the refrigerant than charging the system. Removing air and moisture is done with a vacuum pump. Drawing a deep vacuum boils moisture. Then add refrigerant and recover refrigerant again to dislodge more stubborn water molecules. Vacuum again; then, charge. This level of proper A/C service costs $44.95 plus refrigerant. Vacuuming a system also reveals leaks which can be fixed at the same time to avoid future leak downs. Thanks. David@apexautoaz.com