Question: How do I add a ringtone to my [your phone's brand] phone?
Older phones (and still some recent phones) use a "melody composer." It is a small program that sits within your phone's menu. It lets you punch a ringtone directly on the phone's keypad, as if it was a music instrument.
You can find "keypress sequences" for various ringtones right on this site and all over the internet. Keypress sequences, or "Keypress ringtones," are a series of keys to press (such as "11***") that are pre-coded by amateurs or professionals in order to fit a specific phone's melody composer format. For example, you will see "Panasonic keypress ringtones," "Ericsson keypress ringtones," and so on. This site, for example, offers free ringtones for more than 12 phone brands.
Keypress sequences are useful if you don't know much about music, however, you will still need to have a basic understanding of your phone's ringtone input system. Since each company has designed its own system and since there are so many brands, I can't detail instructions for each on this web site. However, I offer general instructions and all phones with a melody composer have instructions in their owner's manual. If you lost your owner manual, you can still view a web-based version of your manual at your phone's manufacturer web site, in a vast majority of cases.