How to predict expression from histology in unseen samples? What specific input and configuration files should be prepared？

Since I didn't understand how to fill out the configuration file for predicting gene expression, I tried to write my own configuration file (e.g., adding the prediction function in the methods section) and it all failed. Could you please tell me how I should fill in the my-config.toml file or give me an example for predicting expression from histology in unseen samples?