As it was stated before, to create or customize the Customer Portal pages, you will need a WebDAV client to download/upload the files, and you will use a text editor to edit the files. This post shows how to do it.
Step 1: Download and install a WebDAV software. Oracle recommends Cyberduck.
Step 2: Run Cyberduck and open a new connection.
Step 3: Set up a connection to your Customer Portal:
If you input your RightNow Customer Portal site on the Server field, the URL and port should come automatically. Then un-tick the Anonymous Login check box, input your admin credentials and click Connect.
Step 4: Open the folders and sub-folders until you find the file you want to change (in this case we went to the home.php file by navigating to cp/customer/development/views/pages)
Step 5: Select the file you want to change, right-click and choose Download to save the file in your local machine.
Step 6: Open the downloaded file in a text editor, change it and save it.
Step 7: Go back to Cyberduck, right-click the file you want to update and choose Upload.
Step 8: To check your changes open a browser, navigate to your Customer Portal admin site (http://example.rightnowdemo.com/ci/admin) and click View Development Area.
Step 9: Make sure that the Customer Portal you are viewing has the Customer Portal Development Area sign on top.
Doctor CX 
You can use windows 7 natively to do this too as the article on cx.rightnow.com states https://cx.rightnow.com/app/answers/detail/a_id/2600
Thanks Toby, that is very helpful. Cheers!
Hi!, I put in in Cyberduck other files, but when I want to promote them from the Customer Portal the new file is not recognized. Did this happen to you too?
Hi Lara, do you have permissions to CP Edit?
Yes, in Cyberduck I have all change permissions checked, for owner/group/others(rwx).