How do i enter my numeric password in iPhone 4 in VoiceOver mode?
Try triple tapping the home button. 

If that fails you, it might be more involved to rescue the device. 

Either connect the iOS device to iTunes and disable voiceover or learn enough of the voiceover interface to get to settings and change them on the device. 

For many people, VoiceOver is not at all intuitive at first go and really optimized for people that learn how to use it. This learning is an effort unlike the normal iOS interface that toddlers can get with no real training needed. I would say learning VoiceOver is like learning to ride a bike - not hard, but easier if you have someone guiding you or you practice on soft ground while learning and falling.

Tips on using VoiceOver

The touch interface is totally different in VoiceOver. First you have to tap once to select the number, then you double tap anywhere on the screen to select the spoken element.

If your password was 1228, you would:


tap once on 1, then double tap anywhere on the screen to enter 1
tap once on 2, then double tap twice anywhere on the screen to enter 2 twice
tap once on 8, then double tap anywhere in the screen to enter 8


Tips on disabling VoiceOver from iTunes

In iTunes you select summary and click Universal Access, then choose either Zoom or Neither rather than VoiceOver.