giovanni It means that you have to use it on terminal.
$ cpupower --help
Usage: cpupower [-d|--debug] [-c|--cpu cpulist ] <command> [<args>]
Supported commands are:
frequency-info
frequency-set
idle-info
idle-set
set
info
monitor
help
Not all commands can make use of the -c cpulist option.
Use 'cpupower help <command>' for getting help for above commands.