How to use the same file in two projects

Hello

Maybe it's a basic question but I'm quite newbie in E2Studio ... Here I go:  let's say I have developed a project (called A) in E2Studio. I want to create other project (called B) and I need to use in project B one of the functionalities of project A (which is implemented in file X inside project A). I don't want to copy file X in project B for ease of maintenance. Which would be the way to use file X in both projects? Thanks a lot. 

Regards.