How to setup purchased ringtone?

I just purchases a ringtone from the iTunes store on my iPhone 5.
How do I set it up as my default ringtone?
When I go to "Settings", "Sounds" , "Ringtone", it just shows the default tones that come with the phone. It doesn't even show the ringtone I just purchased nor does it say anything about setting a custom tone.
How would I go about doing this?

Applejuiced said:

You're sure you purchased a ringtone and not just a song?
It should show up there.

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Pretty sure. It's the "Big Bang Theory" purchased under TV Star Ringtones and it's only 30 seconds long.
It's not in there.

Applejuiced said:

See if you can plug it to itunes and then go to the ringtones tab.
You might need to transfer purschases from your iphone to your itunes library first.

Click to expand...

Ok I tried that.
It shows up under "Music".
ARGH
Even though I purchased it under ringtones, it's showing up under music!
ARGH!

Applejuiced said:

Damn it, they screwed you

Click to expand...

LOL
Yeah! All of my 99 cents even!

Thanks for trying to help though.
I'll know better next time!