Apple product numpty, so please bare with me

After a faff ive managed to download some ringtones from the internet onto my PC and then onto my iphone 6 in the "Recently added items folder"

I'm buggered if i can then get them into the Ringtones folder on my iphone so I can set any of them as a ringtone though

I'm running version 11.2.6 if that makes any difference

I'm stuck with the crap standard ringtones, whereas I'd rather be listening to a Ferrari F1 engine or a BRM V16 engine when the phone rings


Thanks