[arrrghhh]

Power collapse should happen automatically - when the phone goes into a "sleep" state.

There's this APK called LEDEffects, which will show the LED's on the front to be "breathing" - like the charging state in WinMo. Just lets you know that power collapse is working.

So anytime you turn the screen off on your phone, or if the phone turns the screen off itself from idle time - either way - should go into power collapse mode automatically. I believe if you don't have the "breathing" LED's, then there's something wrong or you don't have the LEDEffects installed (I believe it's built-into these builds, you'd have to remove it yourself...)