Check your server settings tab. There should be a pane in there for logging settings, and you'll want to pick the option there that best suits your needs.
This will make commands echo something like:
(admin) did something to (target)
If you want to see the actual chat message, ie !hp target 100, this should happen automatically. Some commands have the ability to hide these messages, though, and you have to edit core code to turn them back on. I don't recall exactly how to do it, but you probably won't need it—chat logging like the above should be more than enough.
