Compost Friend!

Place enclosure and solar panel in desired locations on bin.
Put sensors in holes that are far away from each other. If you don't already have holes in your bin you may need to make some.
Use a glue gun or some sort of mounting medium to mount enclosure and panel in place.
Glue sensors in place.
Glue various cables so they do not dangle.
Re-attach JST connector to CPX if unplugged.

When placing the bin outside, try a place where sunlight can directly come in contact with the solar panel.

*Consider angling the solar panel towards the sky before installing. This will ensure more direct sunlit hitting the panel. 20 - 40 degrees up from the current position would be a good range.