The ManagerManager plugin will do the job. You should have a chunk "mm_demo_rules" with a few demo rules; most of them are probably commented out.
You can change the chunk to use (or change this one’s name) in the MM plugin’s Configuration tab.
An example of the rules you’ll want to have in the rules chunk:
mm_changeFieldHelp('alias', 'The URL that will be used to reach this resource. Only numbers, letters and hyphens can be used');
To put a link on the Manager’s Home page, edit the assets/templates/manager/welcome.html file. You’ll need to make sure to have a copy of this safely tucked away for after upgrades.
You can also add files to the assets/templates/help folder; each file gets a tab in the Manager’s Help page. The filename is used for the tab title; underscores are replaced with spaces, and the leading digits indicate tab placement. You can look at the existing file to see the internal HTML structure. Usually when I do this, I add a big Help icon and link to the Welcome page as well.