Seeed i2C 4-Channel SPDT Relay HAT for Raspberry Pi

I am trying to configure the i2C relay HAT from Seeed but am not able to find any information on anyone who has done this. The HAT is based on the PCAL9535A processor.

I used the HAAS I2C Configurator to activate I2C, but am stuck on what is next.

Any help will be appreciated.