How to install ringtones for Iphone?

Hello friends
I have a question and want you to help me: I am using an Iphone 7 and how do I want to set my favorite song into an incoming ringtone?
I also went to google to learn a few ways to install ringtones. I used itunes connected to Iphone through my computer. When the ringtone option in the folder in the iphone option does not work.
* An error message: The device is not compatible with each other, while I have completed the process of connecting between the computer and my iPhone 7 device.
I have a question and want you to help me: I am using an Iphone 7 and how do I want to set my favorite song into an incoming ringtone?
I also went to google to learn a few ways to install ringtones. I used itunes connected to Iphone through my computer. When the ringtone option in the folder in the iphone option does not work.
* An error message: The device is not compatible with each other, while I have completed the process of connecting between the computer and my iPhone 7 device.
Comments
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk
Yes, but please keep this to me because there are people who can help me. Thanks admin very much.