Now you can run it and it should be ready to respond to MQTT events. The OpenHAB item and sitemap are defined as:

Switch FamilyRoomLights "Family room lights" (Lights) { mqtt=">[mymosquitto:home/familyroomlights:command:*:default]" }

 Switch item=FamilyRoomLights label="Floor lamps"

Assuming it works, change switch.py to run on startup. You can run this by adding a line to /etc/rc.local. In my case I had to add a "sleep 10" before the command runs in order for it to work properly.

You can also set it to run as part of a startup script in /etc/init.d, something like the way HomeAutomationForGeeks.com recommends starting OpenHAB.