how do i load a ringtone from my pc to my i phone

Buy ringtones from the iTunes Store

1. Open the iTunes Store app.
2. Tap More.
3. Tap Tones.
4. Find a ringtone that you want to buy, then tap the price.
5. Choose an option to automatically set the ringtone. Or tap Done to decide later.
6. You might need to enter your Apple ID password to complete your purchase.

Use tones and ringtones with your iPhone, iPad, or iPod touch

Yes, if you have GarageBand, Transfer the songs/ringtone from Files app to GarageBand then --> GarageBand: Share songs to iTunes - Apple Support

Import a song from the Music app into GarageBand for iPhone ...

Add audio files to your song

1. Open GarageBand on your iOS device, and open the song you want to add an audio file to.
2. If necessary, tap. to open the song in Tracks view.
3. Tap. to open the Loops browser. ...
4. Tap Audio Files, then drag the file to the Tracks area in GarageBand.

Browse your GarageBand for iOS songs - Apple Support