Turn off the circuit breaker controlling the branch lighting circuit. Remove the switch plates. Remove the 6-32 screws securing the old 3-way switches in the device boxes.
Pull the old switches from the box, being careful not to touch their terminal screws.
Check the wires bringing the power from the service panel to the first device box using the digital multimeter. The digital multimeter power switches to the "on" position. Set the meter's function switch to the "AC Volts" function. Touch one of the meter test probes to the black wire, and the other probe to the bare ground wire. If the circuit is safe, the meter's Liquid Crystal Display (LCD) will display 0.000.
Loosen the terminal screws and disconnect all the wires from the old switches. Cut the loops from the ends of the wires with the wire cutters. Remove 1/2 inch of insulation from the ends of the wires with the wire strippers.
Splice the black pigtail wire on the dimmer switch to the black wire bringing power from the service panel. To make this splice, hold the stripped ends of the wires side-by-side and screw on a wire nut. Splice the "Red" and the "Yellow/Red" pigtail wires to the circuit "traveler" wire carrying the power to the second switch. The 'Traveler' wires will be the "Red" and "Black" wires entering the second cable. The cable coming from the service panel will have one black wire, one white wire, and one bare wire. The other cable will have one red wire, one black wire, one white wire, and one bare wire.
Splice the green pigtail wire to the two bare copper wires. Make this splice just as you spliced the pigtail wires to the circuit wires.
Connect all the pigtail wires on the coordinating remote. The black pigtail wire connects to the black wire, carrying the power to the lighting outlet.
Install the switches in the device boxes using the 6-32 screws that came with them. Install their cover plates. Turn on the circuit breaker. You should now be able to turn the lights on and off, and control the light level from either location.