How do I set an iTunes song as my ringtone ?

ok, I couldn't find much info out there about how exactly to do this from an iPhone.. but it was interesting for me to poke around and I think I figured it out.. it's not simple and I've never used GarageBand, so hopefully you're somewhat savvy on your phone and can stumble thru it. Might take a few tries, it did for me and I still don't fully understand what I'm doing. I just know that I was able to get it all the way out as a selectable ringtone.

1. You need to have GarageBand installed on your phone.
2. You need to make sure the song is downloaded to your phone. So go to the Music app on your phone, go to Artists, locate the album you purchased. Make sure it doesn't have a cloud symbol by it. If it does, tap and download.
3. Open GarageBand, go thru whatever introductory prompts they give. You should wind up at a screen that has options of Recent and Browse at the bottom. Select Browse, select On My iPhone, select Create Song, select the empty box with a dashed border called 'New'
4. Now you'll be in a black display with a not much going on.. In the upper right, there is an icon that looks like a looped cable.. click that. Should be a menu up top where you can select 'Music', tap that. Select whatever is easiest to browse to the song you want.. Artist, album, song, etc.
5. This part wasn't super intuitive to figure out, but if you select the song you want and start to drag it, it'll pop back to the black screen. drag the song to the upper left empty box in the grid and release. It will pop back to the song list, just hit done. If this was successful, you should see a jagged blue circle in the box (might need to give it 5-10 seconds to load), if you tap it, should start playing your song
6. Ok, so now you need to take a segment of the song that you want to be your ringtone.. like the chorus of a song. This also was not super intuitive, but while your song is playing.. at least 5 seconds before the part of the song you want, tap the red record button. It will count down 4..3..2..1 and then it's recording. When you get to the end of what you want recorded, tap the red record button again. (From here, you can do some editing, but save that for another time..)
7. in the upper left, there should be a little downward triangle/arrow for pulling down a menu. Tap that, only 1 thing pops up for me, tap 'My Songs'. This will exit you from the 'recorder' mode and it'll save your song as My Song.
8. Now tap Select in the upper right, select My Song, tap the share button on the bottom left (square with an upward arrow), you'll be presented with 3 options. Select Ringtone, rename the ringtone to something that'll identify it easily for you. this will be how it shows up in the ringtone list (name of the song?), then hit Export in the upper right. You'll see it exporting with a progress graph.. next box that pops up just get out of it (don't select 'where to use', maybe try that later)
9. Now go to Settings > Sounds & Haptics > Ringtone > and like magic.. whatever you named it, if I explained thoroughly enough and you followed along properly.. should be at the top of the ringtones list

You need to edit it in GarageBand or iTunes on a computer to crop out the segment of a song you want to use. A ringtone cannot be longer than 30 seconds long.

There are multiple tutorials online about how to do it, like -> https://www.digitaltrends.com/mobile/how-to-make-ringtones-for-iphone/

I definitely wish you luck & success. Hopefully soon you'll be listening to your favorite tune when the phone rings! 😊