First click on an event on the event layer that way its highlighted. Now press F12 and Enter at the same time and then keep mashing enter. The event should open up as well as the RGSS Player.
But wierd thing is y ou edit stuff and then you refresh the game by pressing F12 but it doenst change it. Well first edit what you need to while keeping the game open, then press Ctrl + S to save the game. Refresh the game by pressing F12 now. Load it up and changes have been saved and are now working. This is a great way to test scripts and stuff and if you need to change anything in events for an event system you can change it right than and there.
Have fun
I know I will xD
The neat thing too is you can edit it with three different rgss players open. I just did it but you gotta mash enter after you press F12 and enter at the same time.