how to put incoming caller tune

Do you have that tune among your ringtones on your iPhone?

Should be this case, go to Settings>Contacts>"that contact">Edit... then tap on ringtone (just under e-mail address), then choose your preferred ringtone.

Regards

Giulio

The ability to play music for a caller would be a carrier feature, if it is still done. I remember years ago when these things were offered, but I've not seen anything about it lately. That is not a native feature of the iPhone.