How can I plug an hdmi cable into my xbox??? (read below)?

So I got an xbox 360 slim and on the main power plug (or something) there is a plastic tab that covers the hdmi cable slot... So I did some searching an a couple of people suggested that I remove the plastic cover on the main plug so that the tab doesn't cover the hdmi slot... So I did, but when I try to turn it on with both the main plug and the hdmi cable in the xbox the tv screen just stays black and nothing happens... So I took off the hdmi cable and turned the power on and the xbox worked fine... Help!