Can't sync ring tones to Iphone 6

I purchased an Iphone for the first time (Iphone6) and have not been able to sync any of my custom ring tones. I have used a third party app called Zedge in the past with my google phone and it worked great. With the iphone, I haven't been able to make anything work. I have spent countless hours pouring through other peoples questions and comments and suggestions only to fail over and over again. I have spent time with Apple Care and even they ran out of suggestions. Has anyone successfully been able to sync customized ring tones to your Iphone 6? If so, how did you do it?

Thanks!