How do I open iTunes on a pc ?

See Transfer files between your PC and devices with iTunes - Apple Support. Not all apps support the iTunes File Sharing mechanism. Depending on the source of the data you may be able to save into the Files app which supports iCloud Drive, OneDrive, Dropbox, etc.

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You need to download and install iTunes on your PC:

Update to the latest version of iTunes for Windows 10 - Apple Support

Then an iTunes icon should appear on your desktop. Simple click it.

However, Apple's iTunes software is primarily designed to transfer data from the PC to their devices such as iPhones or iPads but not in the other direction. You may want to see:

Recover your iTunes library from your iPo… - Apple Community