Peel the upper piece of black adhesive tape completely up off the Nexus 7.

Similarly, peel the lower piece of black adhesive tape, but only as far as the copper strip.

It is helpful to fold this piece of tape back on itself to keep it out of the way.

Whilst pulling the tape, be sure that the metal shield does not lift up. Hold the shield in place, and if it lifts up, re-seat it in the spring clips around the perimeter of the shielded area.