How do I transfer music files from my PC to my iPhone 13 Pro Max?

How do I transfer music files from my PC to my iPhone 13 Pro Max? Several months ago, before iTunes update, I was able to simply drag and drop the music files I wanted from my PC on to my iPhone. I can no longer do that. I spent some time with an Apple rep he asked me to re-install itunes and then restart my computer. That did nothing so he told me to contact Microsoft and then hung up on me. So, is anyone having the same issue with iTunes? Why has the simple drag and drop stopped?