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)

He’s one of 3 founders iirc