To hide the row and column headers, simply select 'Hide Row\Col Headers' under the 'View' option in the main menu, located near the top of the SpreadsheetLIVE user interface. Once they are hidden, the option will change to 'Show Row\Col Headers', if you decide that it's preferable to see the row and column headers. They are highlighted below.
Image 1 - The 'Hide Row and Column Headers' option under the 'View' option in the main menu and the row and column headers highlighted in the user interface.