.net core App configuration settings for referenced projects

I am new to .Net core. i have few issues

1. I have a different project which i am referencing here by dll. in that project am reading password and other keys from the app.config file. i need this .net core project to pass the values for that app.config, using the regular configuration manager to read these values in the the external project.

can anybody help with setting up the app.config in .net core 2 so that other external project with .Net Framework setup can access values from configurationManager.