How exactly do I setup the double spend transaction?  I am a bit confused on this operation.  There are three fields I fill out during a send 1) Amount, 2) label, 3) address .  The transaction fee is injected by Multibit.  How exactly should I populate the double spend ? Also, do I need to send from the same computer or any computer with a copy of my wallet? (one runs multibit .5.18, the other is running version .5.19)