If you're like me and don't like the selection of the SMS ringtones pre-loaded in your phone, you can add ringtones of your choice in manually. I download my ringtones from Zedge, as everything there is totally free. One thing that you have to remember though, is that when I refer to a ringtone, I am acutally referring to a notification tone. A regular phone ringtone will work but it is just too long to be a SMS tone. A notification tone is different because it is only 2-3 seconds long. So when doing your downloading, make sure that it is a notification tone and not a phone ringtone.
After you download your notification tone to your phone, go to the folder that it was downloaded in using your file manager (my folder is Zedge):
Once you are in that folder, press and hold the notification tone that you want to highlight, then select copy from the settings menu (I selected Car Lock):
Then go back to the main folder menu in your file manager, and go to the Notifications folder. Once in there, select paste from the settings menu... that's it.
To set the notification tone, click on your messages app, and in the main SMS page, go to settings. Scroll down, and from their you can select the notification tone of your choosing