The fitting in the pic is the high-side fitting; charging is done through the low-side fitting below and to the rear of the air cleaner inlet duct.

The only really correct way to charge the system is by weight (the amount is on a decal under the hood) and it helps to have a gauge manifold/hose set (available cheap from Harbor Freight) and the pressures on the gauge set will tell if the charge is low.

With the manifold set you can top off the charge by temperature/pressure but it's not as precise as by weight.