Adding new field

Hi,
So the current tasks module has the Contact name field which has a arrow button navigating you to the list of contacts you can choose from your system. I want to do the same thing but for Opportunities. basically having a “opportunity name” field and an arrow next to it allowing you to choose from your existing opportunities. Any idea how to do this? thanks!!

I think that you just have to add a one to many relationship between the two modules.