There is no valve for adding freon. Strike that, R134a is not freon. Freon was a trade name for R12. Use a manifold set connected to low and high side and monitor both. Charge through the low side.

DO NOT USE A DEATH KIT!!!!!!!!!! This is the cheapie green zone, red zone gauged can from your local store, referred to in this thread as a DIY kit. Monitor BOTH sides and charge properly. If there are questions, take high and low side readings and post them here along with ambient temperature.