keyless entry reprograming HELP!!!!

I have a viper alarm, its kinda older. It has the I and II buttons on the remote. I accidently messed with the vallet switch. I need to reprogram the remote. I heard these instruction

1) turn key to on position
2)push vallet switch
3) press arming button

This does not work, can someone tell me how to do it in detain. Plz help!!!