Ratgdo and ESPHome integration failing due to API problem

I have the ratgdo v2.0 on ESP8266(?) , and am running into a problem in the ESPHome integration in HA. It sees the device but when I configure and hit submit it chokes and says the api needs to be added to the ESPHome config file. Where is the file, how do I access, and what code do I include? Also, can the ratgdo be upgraded to v2.5 or is that a hardware thing? TIA.