If you are looking for a command to perform a specific action, it might already exist in PhantomBot. The first and best place to look is the command list:
In the Search box on that page, you may search for keywords that will match modules, commands, usage for commands, and description of commands.
Please note that if a specific command is not available, you may need to enable the module. Either find the module mentioned on the commands page in the Control Panel or run the command. Note that if you click on the module name, it will be copied to your clipboard on the commands page:
!module enable Module_from_page
!module enable ./systems/quoteSystem.js