How to create plugin/add-on which will execute with MSFS?

Hi, just quick question: how to create plugin that will execute with MSFS or with new flight? I’ve been creating external apps using simconnect for few years which worked fine but I’ve never tried creating plugin. Is there any tutorial or example for creating and adding it to msfs? I assume that I need to create dll but how it should look like? How it will be called?