Follow the instructions in the Solar LiPoly Charger Guide, but when it comes time to solder in the capacitor, bend it over so it lays down on the board first. This will help it fit better with everything else inside the enclosure.
Assemble the MintyBoost as instructed, but lay down the tall capacitors and boost converter before soldering.
Instead of soldering on the MintyBoost's battery holder, solder on the JST cable that comes with the solar lipoly charger kit (red to + and black to -).
Plug the MintyBoost into the LOAD port on the solar charger, and plug a lithium polymer battery into the BATT port. Test that your MintyBoost is putting out 5 volts, then unplug the MintyBoost and solder on the USB jack as instructed.
The solar charger has an output as high as 6V, this is a little higher than the Mintyboost is designed for but will work. The output voltage to the USB may end up at 6V. If you want to keep the Voltage out at a 'strict' 5V, connect the mintyboost to BATT not LOAD from the charger.