Step 4: Add the solar cell
The second method is to replace the connector with another JST connector and plug it into the third connector marked 5v on the charging circuit. I didn't have another JST connector handy so I just soldered a salvaged two pronged connector to the charging circuit where there are two open pins on the 5v line.
Using the second method certainly is a bit cleaner since you don't have the big barrel plug sticking out of the side of the tin.
UPDATE- Since the original charging circuit has been discontinued, the best way to connect the new version Sparkfun LiPo charger is to splice a mini USB cable to the solar cell wires so it can plug directly into the charger. There is a simple guide on how to do this here-
Now attach the solar cell to the top of the Altoids tin using some 2" wide Velcro. I wrapped the battery pack with a layer of clear packing tape to help protect it. Then the battery pack is simple set down on top of the two circuit boards- it's a near perfect fit.
Now set your MightyMintyBoost out in the bright sun and charge it up! You should see a little red LED on the charger board light up. Once it's fully charged connect your iPod/iPhone/USB powered device and enjoy!