hello, how download ringtone on iTunes?

Note that since the release of iTunes 12.7, iTunes on computers is no longer used for ringtones. See the following: Changes in iTunes 12.7 - Apple Support

You can purchase a new ringtone using an iPhone: Open the iTunes Store app, tap the ... icon, tap Tones,

You can download a previously purchased ringtone again: See the following from Use tones and ringtones with your iPhone, iPad, or iPod touch - Apple Support

With iOS 11, you can redownload purchased tones that you bought using your Apple ID.

Go to Settings > Sounds & Haptics, then tap on any sound. At the top of the page, tap Download All Purchased Tones to check for any previously purchased tones not currently downloaded to your device. You might not see this option if you've already redownloaded your purchased tones or if you haven't purchased any tones.

You might not be able to redownload some previously purchased tones.

See iTunes - Working with iTunes - Sell Your Content - Apple.

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