So this is what you need. Clearly I got my screwdriver at Winks.
If you flip the dock over it looks like this. Notice the 2 cover plates. These will hold the Lightning cables in place.
Unscrew the the 2 cover plates. Don't loose the little brass plated screws!
Put the cable in like this if you use a "naked" iPhone.
The cover plate has two different sides. Put the Lightning cable in like this if you use a case on your phone. Not all cases fit the dock, so try it out first (after taking the black bar out).
Force the cable into the slot. This may take some force. Make sure it is flush with the cover plate and straight.
Do the other one as well, and put the to the dock.
Just like this.
The top should now look like this.
Screw the cover plates back on. Not too tight though.
Push the cable towards the oval and start guiding it into the slot.
This one goes 1 1/2 turn clock wise.
This one goes 1 1/2 turn counter click wise.
Take a bar from the top. Btw, if you use a case in your phone these bars come out.
And use it to push the cables as deep into the slot as possible
Just like this. Thus will also hold them in place.
Maybe push the cables here down as well.
Put the bar back in.
Done! Now go get a second iPhone :-).