To modify the default login page so that it has the RT login instructions that your users are familiar with, you need to edit a language string. Go to Administration>>> Site administration>>> Language>>> Language customisation.
Choose English, then Open language pack for editing and then click on Continue.
Select the component Core: moodle.php and in the String identifier field, type login_desc. Then click on Show strings. The Standard text field is empty by default. In the Local customisation field, enter the following HTML (you can copy and paste this code into the field):
<h2><font color="#151B8D">Returning to this web site?</font></h2>
Login here using your username and password<br>
Cookies must be enabled in your browser)
Click on Save changes to the language pack. You will then see a message that “There are one modified strings. Do you wish to save these changes to your local language pack?”
Click on Continue to save the change.
When you log out, you will see the new text on the login page:
You can, of course, modify the string as appropriate for your site.