Howard Miller

I'm struggling to understand what part of this makes you think you have to type it on the end of a URL? Anyway, to answer the question you asked (which may not be the answer to your problem)

* Go to Site administration > Users > Define roles
* To the right of 'Authenticated users' (role) click the edit cog
* Find the Filter box and type 'sendmessage' in there
* Make sure the capability moodle/site:sendmessage is enabled / ticked

As it's on by default, I would be surprised if it is not.

It's a capability. It's part of the roles system.

I'm going to encourage you to read Roles_and_permissions, rather than "spoon feeding" the answer. It's a powerful system and worth understanding how it works.

You might want to look at Custom_reports. Unfortunately, on 4.1 it's quite limited - much improved by 4.4.

Failing that, if a (mostly) one-off I would probably get this directly from the database. That rather hinges on your SQL skills, knowledge of the database and/or how much you'd like to learn that stuff.

It might help to tell us what "VidGrid" is and how this has been integrated with your Moodle site?

Ahh.... good spot. Not being a user of this stuff probably explains why the question made no sense to me at all