The AB Electronics UK Knowledge Base provides support solutions, tutorials and troubleshooting guides.
The Expander Pi uses the same real time clock as the RTC Pi and you can use the following tutorials for using the RTC with your Raspberry Pi.
RTC Pi on a Raspberry Pi Raspbian Jessie and Stretch
RTC Pi on a Raspberry Pi with Raspbian wheezy
RTC Pi storing double values in RTC memory
RTC Pi storing integers in RTC memory