Go to the Admin -> Permissions -> Permissions Group menu;

Click on the "Edit" button for the Default permission group or if you have created other permission groups, select the relevant permission group and you will see this page;

Click on the "+" button in the Direct Message block;

You will see this window pop up, where you can add "sms" to the "can send" option and then select who the users of this permission group can send messages to. The options are "all users", "all users of own role" and "all users of selected roles";

This highlighted inset shows the options. If the third option is picked, you will then be able to select the roles as well;

To add or change messaging permissions for a specific user, go to the Staff menu, select a user and you will see this page;

Select "Permissions" and you will see the default permissions in the middle and the additional permissions on the right hand side;

Click on the "+" button in the Direct Message block;

You will see this window pop up, where you can add "sms" to the "can send" option;

You can then select who the users of this permission group can send messages to. The options are "all users", "all users of own role" and "all users of selected roles";

If the third option is picked, you will then be able to select one or more roles;

To view the messaging permissions for a specific user, go to the Staff menu, select a user and you will see this page. Select "Permissions";

The default permission group is shown in the middle;

Any additional permissions given to the user can be seen on the right hand side;