I don't think anyone here is going to tell you that. I am sorry, we can't tell you how to harm yourself, only to give emotional support. And beleive me, there's tons and tons of it here.
I can understand the limbo you are in. I myself feel that I have to die because I feel that my life will always be awful, but yet I am also very afraid of death and what happens afterward, I myself feel just trapped.
My counsellor once suggested an alternative to self-harm is squeezing a handfull of icecubes, straight out of the freezer. It's still unpleasant and a strong sensation, and lets you get a 'release', but doesn't cause any physical harm.
Perhaps you could try that before you resort to something else? I sometimes hit pillows, shout into them or grip my wrist/arm really tight and squeeze to try and let some of the pent-up stuff out. Afterwards I usually feel more relaxed, and tired, and less likely to self-harm.
i am not in a position to TELL you how to harm yourself and neither will i ever. it is not worth it huni... the ice cube thing that stray kitten suggested is very good. try that or try venting your anger by writing it down. it is a very therapeutic way of helping yourself to gain control over your life once more.