96 Grand Am - Help adding R134A

We have purchased the kit to add R134A but the connector doesn't fit securely on the port. Either it is not the right port or place to connect the hose or there is a trick. Any help is appreciated.

THere are two service ports. One is on the high pressure side, and one on the low pressure side. They are different sizes. The valve up top near the radiator is the high side, which is not the one for filling. The fill port (low side) is on the metal line right off the compressor. It appears you'll have to access it from underneath.