Molex is basically two styles of retainer.
On one, there are two little arms on one of the connectors and two usually square open bridges on the other side, the arms have half an arrow head on them, and go through the bridges to lock them together.
Squeeze the arrow heads towards one another and pull the connector apart.
On the other style, the half arrowhead arms go inside the other half of the connector and expand outward to grip.
Again, squeeze the arrowheads toward one another and pull apart the connector.
Now if you get to some of the European styles, those things are a real pain in the @$$. Some I have worked on require you to squeeze, while pushing down and turning, then continue to squeeze, and turn and pull apart.
Those are usually so far inside the machine you can't see them easily, nor can you get your hands in there to separate them.
The later style of Molex are the easiest, those have a pivot in the middle of the arrowhead arm, squeeze the outboard end of the arm and the half arrowhead that looks like the extractor on a .22, lifts out of it's notch and a tug and the connectors are apart.
Easy to get to, and you can both see and feel when the arrowhead is free, as the outboard end of the arm bottoms out against the connector shell. When that happens, you know the arrowhead is out of its notch.