My last phone was a Motorola Droid (1) and when I wanted to get new ringtone, notification, and alarm sounds all I had to do was create a folder called "media" and then subsequent folders for each different sound category. I tried directly copying this folder from my old Droid to my Bionic and it works exactly the same. I just figured I would pass said information along for everyone to have at the ready if this is your first Android phone.
Plug in your phone to your computuer
Create a folder in the main directory titled "Media"
Create the following subfolders in the "Media" directory:
Create or place any sound files in their respective folders to have them at the ready for your phone. You can use a program like RingDroid on the phone itself to create tones of Audacity to cut music on your computer.
Note: if you want a file to be available for a ringtone AND an alarm, it must be located in BOTH folders.