Apps, if u don't mind I can take this one. He means that in ISBoxer, he made activate slot 1= F1 and activate slot 2= F2.

As a side note, if ISBoxer has a hotkey assigned (F1 for example) when you press F1 ISBoxer kinda intercepts it and uses it for itself. SWTOR the actual game would never know that you just pressed F1 since it is already assigned as a hotkey in ISBoxer.