E66

Using your phone's cable, connect your phone to the USB port of your computer.
Your Nokia E66 will ask in which mode it should connect to the computer.
Choose Mass Storage.
YOur phone will appear as a new removable drive in My Computer.
Copy the audio file from its location into Sounds->Digital-> and go to the last folder from the path.
Disconnect your phone by choosing "Safely remove hardware" from the bottom right corner of your computer's taskbar (Windows).
On your phone, open the Main Menu.
Select Media.
Select Music player.
Select Music.
Choose All songs.
Scroll down to locate the audio file you just transferred and select "Options"
Scroll down till you find "Set as ringing tone.