Oh sure, I'd love to help. (Although it's not really my hack, Mildmojo wrote it.)
So when you download your game from the bitsy page, you get a .html file. To make the hack work, you need to open that file in some text editor and paste the code of the hack in its own script tag. Like this: "<script>[the hack]</script>" Putting it near the end of the file, right after the last </script> tag, seems the most reliable.
To use the hack, just add exit commands to the dialog of some sprite. It can appear anywhere in dialog, and should look like this: (exit "roomname, x, y") Just replace roomname, x and y with the value you want. using exitNow instead of exit will move you instantly, instead of waiting until the dialog is over.
If anything's still unclear, don't be afraid to ask!