How to add interactions to custom objects?

Hi. In short:
- find a maxis item that functions in a way you want yours to function;
- copy its tuning related data;
- paste it into the same fields;
- if you want to modify the functionality further, you create a unique tuning based on it.

This two tutorials should give you an idea of what to do. For more advanced info, it is best to join discords of experienced modders, they tend to have tutorials
sims4studio.com/thread/1324/make-basic-change-items-tuning
sims4studio.com/thread/20149/creating-animated-objects-interaction-tutorial