To enter owl's command mode press the colon (:) key:
: begin command mode
Owl will give you a command prompt and you can begin typing your command. Type Enter to execute the command, Control-C to cancel. The basic commands are listed on the basic help screen (by pressing h).
For detailed information on the syntax and use of a command you can use:
help command
For example help zwrite will display all the options available when using the zwrite command.