Assembling the rpi+rpi ui case.
To assemble your rpi+rpi_ui case you the following procedure is the easiest.
Use the screws, the MDF spacers, and the long bolts to connect the raspberry pi to the baseplate of the case. Add the rpi_ui onto the raspberry pi with the spacers. Alas, you cannot do this if you have a V1 raspberry pi. There are holes in the rpi_ui display to bolt the display onto the long nuts that we've just placed. Alas, it is impossible to get a screw through the hole below the display. And the other screw-hole interferes with the jumper block that might be present there. You can chose to put just a short piece of M3 thread into the hex pole, so that at least the position is fixed. In case you want the jumper block installed, you can cut off the side of a nylon M3 bolt to make it fit next to the jumper block. (If you want to do this, you have to screw the nut to the rpi_ui first, and only then add the rpi_ui to the raspberry pi and then finish screwing in the screw from the bottom for that position. )
Next we can start to assemble the case. Find the two small "lock" bits and place them into the bottom on the side that has the RPI's HDMI connector. Next slide the top of the case around the display and put the "lock" parts into their slots. Next add the side of the case which has the HDMI connector cutout. Take care to place it the right way around. Now you can add the screws to keep the lock parts in place. Please be careful: the plastic is not able to withstand the big forces you CAN apply with a screw. I recommend that you don't tighten the screws all the way. This allows for some play during the rest of the assembly. But even then, the case is already starting to get some form.
Next you need to add the lock on the side with the TV and audio connectors. The next step is to add the USB/ethernet side of the case. And the usb-power and SD-card side. Then the last side of the case slips on and can be tightened with the third screw.
Now you can finish tightening all the screws.