How do you retrieve purchased ringtones

When you purchase ringtones, you need to download them to a computer with iTunes, or "transfer purchases" from your iphone to the computer. Then they are backed up, and can be reinstalled if deleted. Otherwise, you will need to contact itunes support with the order number used to purchase the tones and ask for a regrant. Ringtones are ..... very short lived in the iTunes store - so they don't stay available like most music.

Retrieve them from where?

They will only be where you put them.