Step 5: Make it! Solder it! Part 3
Once the electrolytic capacitor is in place, insert the 3.3V regulator and the smaller ceramic capacitor as well. The small ceramic capacitor helps filter out high frequency noise from the power supply and the regulator turns the 5V input into a nice & steady 3.3V that the XBee requires.
The ceramic capacitor is non-polar, so place it 'either way'
The 3.3V regulator must be placed correctly, but is easy to do: simply match the shape on the silkscreen with the semicircle of the regulator.
Make sure the capacitor and regulator sit close to the PCB, especially if you're planning to use an XBee Pro module.
Now solder in the power supply components & clip the leads
Next is the buffer chip. This chip converts the 2V-5V signal from the bottom strip of pins to 3.3V so that you can safely connect the XBee to 5V logic circuitry. If you're planning to use the two lines of parallel breakout pins instead of the lines at the bottom of the PCB, you may want to skip the buffer. However, most people will want it in place
The buffer chip must be placed in the right way for it to work. Look for a U-shaped cutout notch in one end of the chip. This notch should match the U-shaped notch in the silkscreen. See the picture to make sure its in right.
Flip over the PCB and solder in every pin of the buffer carefully. The pins will not have to be clipped once they are soldered in