I'm not really sure i understand the problem, are you running into problems getting the url for the registration page to include in the text

Have you set the "User Page"  value in the Page Management settings on the Site Settings tab of the admin menu. In there you can set the page that users are directed to. Its usually a page with the "User Account" module on it

You should be able to just copy the URL for the page with the "Preferred User Information" from the browser address bar, paste it into a word document or notepad then just add the text and insert the required URL as normal in the given module.

Let me know how you get on

DNN allows you to set specific pages as the login page, user account (registration) page and search results pages (I'm using DNN Version 4.5.1 so you mightn't see all those options in the page management section). This feature allows admins to add the specific modules (Account Login,User Account and Search Results) to the relevant pages as well as any other modules  they want and design the look of those pages as well as maybe hide them so they don't appear in the menu listings