First off, do it when you have time and good lighting. Easy enough, but don’t want to break it.
In a nutshell, the red part gets released by the black tabs on the sides.
It is this part (red) that locks the pins in.
The book says to twist and pull to remove wire.
I find it better to go a step further and remove the red piece completely, so as to see the release inside.
Then you can see that the new pin is inserted correctly.
Snap it back together and done.