How can I get MP3 files from a ripped CD onto my iPhone?

You should be able to drop them to your iPhone through iTunes. But iTunes no longer exists on current versions of iPhones. Everything is separated into the Apple TV (for videos) and Music apps. If it's dropped it should be available in the iPhone Music app under "Downloaded" songs in the library.

iTunes has been split up into 3 apps: Music, Podcasts and TV. Your synced tracks will be in the Music app on your iPhone. But iPhones can’t play MP3s. CDs must be imported to iTunes using a supported iTunes format such as AAC or Apple Lossless.

Sure. But I recall that was where songs transferred over from a computer were playable regardless of the source. But of course it got interesting because ripped songs were generally available for listening through streaming, and still are through the Music app. Not sure how that works in terms of licensing.

The iPhone music app, whether it was called iTunes or Music has never been able to play any format other than AAC or Apple Lossless. But when you use iTunes to rip a CD it doesn’t create an MP3, it creates AAC. If you subscribe to Apple Music your phone will play the streamed version of your CDs.

Lawrence that is not correct, the iPhone app could play a number of formats including MP3 but only with certain bitrates. I also had problems with odd bitrate settings and variable bit rate with MP3. You could rip music in a variety of formats and sync them to the iPod or iPhone. When you rip to iTunes (or now Music on the Mac) you can select the format you want it to be in. If you purchased music from the iTunes Store it was in AAC or later lossless.

Import them into iTunes on your computer (Or Music on a Mac), then sync the phone to your computer.

I'm not sure what you are referring to about accounts. Do you have a current version of iTunes and a music library on your PC?

You don’t need iTunes on your iPhone (it never was available for download) you need iTunes on your Dell PC and it is still available. None of those apps apply to your situation.

The only iTunes that was ever available on iTunes was purely for purchasing and playing songs it never did allow ripping songs and altering formats. It has been gone for quite awhile.