It depends on how you created the project - did you copy it out of the library or did you generate an initial project based on the I-CUBE-LW library or from the STM32L476 board?
If you used CubeMX then the .ioc is generally in the top level of the project folder and is listed in the file browser in CubeIDE.
As well as defining the IO, you’ll need to add the drivers for the sensors and then some code to read the sensors and then add them to the payload.
You say you are now sending dummy data and temperature values - this implies you have already found the place where the payload is constructed.
I’ll be happy to assist with this, I am quite familiar with the I-CUBE-LW setup, but first I’d appreciate an answer to Porting STM32WL LoRaWAN to STM32L476RG - #5 by descartes so that I have some context.
It would also be useful to know if you’ve used STM32, LoRaWAN and LoRaMac-node before.