To get the achievement, you have to close the game if you are in i, look for the file in the steam folder, mine is C:\Program Files (x86)\Steam\SteamApps\common\The Stanley Parable\thestanleyparable\cfg.
Make a new line and put in this.
bind "x" "~;_u"
It's easier to copy and paste.
Save it, right-click and click properties.
Set it as read only so it doesn't change it.
Go into The Stanley Parable.
Play.
Press X.
Wait a few seconds.

I'm not sure how the achievement was suppose to work, but supposedly, a patch was released that made this work.
Hope this helps!