Found this on the net
On 28" wide cabinets the channel is about 11.5" from the left side.
Get a ~3 foot long piece of 1/16 x 1" flat bar and shove it in on top of one of the drawers slightly to the left of center until it hits the back panel. Make a mark on the bar so you know you are over the drawer back wall.
There's a stiffener channel that runs down the center of the cabinet back panel, so go about 1.5" to the left.
Then slide the bar to the left, keeping it parallel with the side.
You'll feel the locking channel. Probe around a bit so you can visualise its location.
The lock channel is somewhat like a C channel that rotates around a corner of the C shape.
When you locate the right hand edge of the lock channel, pull the flat bar out about 1-1/4".
Than push firmly to the Left, keeping it roughly parallel to the side. You need at least a foor of flat bar sticking out of the front of the cabinet to get enough leverage.
Keep in mind you are trying to rotate the channel clockwise viewed from the top of the cabinet.
You should feel the channel move as you push to the left. It'll click to the open position with a positive detent.
Your drawers should open.
You may be able to get access through the bottom of the cabinet if you lift it up, but it depends on your cabinet. Mine has small access holes at the back.
Call Lista and they will email or fax you the instructions for the type of cabinet you have. It has a drawing of the mechanism so you can see and understand what you are doing.