Hello!

Unfortunately, when I updated the controls, I forgot to update the tutorial. To open the door, put the key in the left hand slot in your inventory (that's the slot on the left). You should see the key in your character's hand in the 1st person view. Aim the crosshair at the keyhole and click. The door should open and the key should disappear.

I hope that helps! There are lots of other portions of the tutorial that are out of date. I've updated them on my end, but it's going to be a while before the next update. Hopefully, once you get the hang of it, the controls should be somewhat intative.

Cheers!
- Bret