Step 17: Wire Everything Else
If your case is conductive, you only need to connect one pin from the jacks to ground. The other pin will make a connection through the case.
That said, make sure you connect the input and output jacks appropriately. In case you don't know what appropriately is, the input and output pins should be connected respectively to the center pins on the DPDT switch. One outside pair of pins should be connected to the circuit board (paying careful attention to "In" and "Out"). The other set of pins should be simply tied together for true bypass.