[otrs] changing things in otrs

Hi All! I'm trying to make some changes in OTRS, but can seem to get started. Whatever i do it doesnt seem to change anything in otrs at all. For example if i try to edit Output/HTML/Standard/AgentZoomHead.dtl and comment this line out: # should we show the close action #$Text{"Close"}</a>"; }> I expect the close button to not show up anymore, but nothing happens. Any help to get started would be welcome. Cheers.