This step covers how to solder the oscillating crystal to the real time clock and how to wire the real time clock to the Arduino. The data sheet for the DS1307 real-time clock can be found here
First trim the legs down on the real-time clock so that they don't poke other parts of the watch.
Then solder the 32kHz crystal to X1 and X2
The SCL is soldered to A5 and SDA to A4 as shown in the soldering chart from the "Soldering Connections Diagram" step. Then solder the power to Vcc and ground to ground.
At this point the Arduino Watch is fully functional for the basic functions, so power it up and test it out! If the clock doesn't run try power cycling and/or use the reset button on the Arduino. Sometimes it takes a couple cycles to the the real-time clock going.