Then locate the shelf where the item is stored. Touch the two stop signs which are illuminated either side of the section you need so that they go from red to black. Press the arrow facing the shelves you wish to access.
Please note that occasionally several stop signs may have been activated in the shelving block - you need to switch off all stop signs before the shelves will move. To switch the stop signs off simply just touch them.
If you have problems ask for assistance at the enquiry desk on the floor.