[Gretl-users] Using functions

Hi I am new to Gretl so still a very basic user. From the Function Reference help menu, I saw there is a ljungbox function. I would like to use this but when I enter the function into the console window using the series name and lag, nothing is returned, just a blank line. The same happens with other functions listed under Statistical in the help menu. I have looked through all the help menus and manuals but can't find guidance on how to run these functions. Please provide instruction for how to use these functions. Thanks Leon