The first thing to do is to physically mount the screen onto the main board, and this is done by putting a piece of black tape down each side of the screen and wrapping the tape around to the back of the main board.
Turning the main board over, you can see the three connectors from the screen which must be attached to the main board. The wide one with the bar code controls the e-ink display itself. The one just above it (with a chip that you can't see at the moment) is the touch screen input, and the small one with the "K4J" label sends power to the LEDs that light the display up.
The next image shows the connectors when they are plugged in. The touch screen cable is inserted by putting it just into the socket, and then using a thin flat screwdriver on the white strip (which you can just see poking out on the left of the socket) to ease the connector fully into the socket.
There is a trick with the other two sockets which I only learned today, and which is why I had so much trouble when I did the teardown. They have a little "flap" which you raise to insert the connector, and then lower to lock the connector in to the socket.
Below is a photo with the flap raised on the long socket.
And here is the same socket with the flap lowered. You can also see the small socket which I previously damaged trying to get the small connector in when the flap was down.
So, the right way to do things is to raise the flap, then insert the connector.
With the connector inserted, use your fingers or a screwdriver and close the flap (like turning a book page) to close it.
Here is a photo of the screen now working correctly, but before I put the device back into the frame. The LED lights are on.
And here's one with the LED lights off.
Warren Toomey, October 2015.