I agree that the antenna installation should be included in the manual. Here's what I did (might be completely false, but both WiFi and Bluetooth work for me):
 
First remove the screw that holds the plate and the m.2 wifi/bt card and remove the card itself. Than take your two antenna cables and put them on the links on top of the card. There is no dedicated WiFi or BT cable nor slot, so the order does not matter. How to join the cables? Well, I have no good advise on that, I was just playing with it until they snapped into place. Some pressure might be required.
 
After that, put the card back to the board. For the antennas, you will find 4 additional component: 2 spacers and 2 female screws. Put the spacer on the connector than put the connector through the IO shield (so the spacer is inside the case) and than screw the female screw on the connector (so it will be outside the case). Tighten the screw really well! If you don't, when you are putting the antenna on the connector, you will end up rotating the connector (and as a result, the antenna cable too, that looks really fragile to me) instead of tightening the antenna. I used a torque wrench.
 
I hope this help somewhat. Good luck and please get back to us with your experiences.
 
Best Regards,