First, install all of the through-hole components:

• The 4 position DIP switch. Install the “on” side towards the top.
• The pilot screw terminal. Insure the wire openings face out over the edge of the board. 
• The switch 2 pin header.
• The blue 2x3 ISP header. Place the notch on the side of the board that has the square pad (pin 1).

Solder one pin of each, verify that the part is oriented correctly and is flat against the board, then solder the remaining pins

Insert a nylon bolt through each hole in the corner of the display from the front. Carefully place the display face-down on your work surface. Position the 16 pin SIP header in the pins on the display (it doesn't matter whether it's the long or short side). DO NOT solder anything yet. Place a standoff over each bolt. Place the control board part-side up over the display, insuring that the bolts go through the matching 4 holes and that the pins of the SIP header protrude through the matching holes. Thread a nut over each bolt and tighten. Once you've verified that the two boards are physically mated together properly, solder each pin of the interconnecting SIP header to both boards.

Power the tester with 6-12 VDC, center-positive. Rotate the contrast pot almost, but not fully, counter-clockwise and adjust for best display contrast.