me_irl

the iTunes Store app on your iPhone should let you buy ringtones! in the … /More menu at the bottom, then "Tones".

edit: good god the selection there is bottom of the barrel. good luck!

In the iTunes app click the [… More] on the bottom right and select Tones. To set them open the settings app > sounds & haptics > ringtone (there’s also a link to the tones store in there)

There’s also a ton of apps/websites where you can download a larger variety and even make your own, like Zedge (searching ‘ringtone’ in the app store finds a ton)

There’s also a way to do it for free but it takes like 5ish minutes rather than a few seconds. It involves using the garage band app so you can probably find a tutorial on YouTube. Otherwise, just follow what everyone else has been saying to but it if you don’t wanna do that.