If this a first generation 922 then you just insert the rounds into the cylinder, there is no cylinder gate. To unload it push the latch under the cylinder pin, pull the pin out, and then remove the rounds using the pin. Or you can do as I do and just use a thin screw driver to empty the cylinder.
If this is a 2nd generation 922 then it is a swing out barrel. To load/unload pull the swingout arm pivot pin towards the front of the barrel and tap the barrel which will swing out.