I wrote a little
guide for this ages ago, but it seems to have vanished.
The connectors lock very firmly together and the locking clip isn't always obvious. In the example below I've used the brake fluid cap as a subject, because it's easy to see and it's yellow.
The assembled connector looks like this
You need to pull the locking clip backwards to release the connector.
The disassembled connector looks like this.
End-on, the wiring plug shows a bit more detail of how the locking clip is formed.