So the questions are: what does "activate" mean? And how do I activate?
Ok, you're running the 4.0.0 GUI. And you're referring to an unclear tooltip that seems to mean "double click or hit enter to open this file in the editor, right click for other options"
Does anyone know if this is still the tooltip in 4.4.0? A lot of code has changed since this version was released.
So the answer is ignore it and we recommend upgrading.