Hi funzotothemax,
As of January, The Echo Nest no longer has song identification capabilities in our APIs -- there is not any way to ask The Echo Nest to identify an audio file that you have locally.
This thread, where we announced the suspension of the song/identify API, includes notes from a couple other services who are trying to provide these capabilities, though. Maybe start by getting in touch with them.
But this would still be the building blocks to do what you're asking, not a finished product. Even if you find a service that lets you upload audio (or run a fingerprint of the audio on the local file and upload that) and get back information about artist, track, etc, you need some piece of software to scan your files, fingerprint them, upload the fingerprints to the service you find, and then turn the results into tags in your local files again. The Echo Nest has never provided such a thing and I don't know if it exists. It might be a fun project to use to learn how to program, though!
-Eli