Code:
on *:JOIN:[color:red]#channel[/color]: { /notice $nick Hello!welcome to the chat. make sure to read the chan rules by typing !Rules. If you need any help with some of the commands in IRC Type !Help. Feel free to send me a PM if you need somehelp thanks ^_^}

on *:TEXT:[color:red]#channel[/color]:!help*: {
  what to happen
}

Replace the red part with the channel you want it to show on..

or you can also use:
Code:
on *:TEXT:[color:red]#channel[/color]:*: {
 if ($1 == !help) { what to happen }
 else if ($1 == word) { what to happen }
 else if ($1 == word2) { what to happen }
 else { return }
}