Steps to Send a Patch for a New Feature?

[Wamm K. D.]

'Ello, Emacs.

A few years ago, I was adding a feature to a library, before it was part
of Emacs proper, and ran head-first into a brick wall of executive
dysfunction.

In the time since, the library was added to Emacs's source; I have the
bulk of the work done as the only remaining thing the author wanted was
another example of the new feature I was adding but I'm unfamiliar with
the process to send a patch for Emacs.

Any help is super appreciated!