How to generate installation code to connect zigbee end point to coordinator with energy profile 1.x (smart meter)

I like to make a device to monitor smart meter installed in Texas. Per utility companies, smart meters are set as coordinator with zigbee smart energy profile 1.x, and to pair it with a monitoring device, customers should email them MAC address and installation code. I am familiar with MAC address, but what is installation code, and how can I generate it?
Thank you.

An installation code is used to create a preconfigured, link key. The installation code is transformed into a link key
by use on an AES hash. For more information and sample code, consult the ZigBee Smart Energy Profile Specification (ZigBee Document Number 07-5356). Public access for ZigBee Technical Documents can be found at:

Digi does sell Smart Energy routing gateways which support Smart Energy profile 1.x and have install codes pre-programmed.