If you’re looking for a way to download YouTube mp3s onto your iPhone, there are a few different ways to go about it. You can use the YouTube app on your iPhone or iPad, or you can use a third-party app like iMovies. To download YouTube mp3s using the YouTube app, open the app and search for a video that you want to download. Once you’ve found the video, tap on it to open it in fullscreen mode. Then, tap on the three lines in the top left corner of the screen (known as thumbnails) and select “Download MP3.” To download YouTube mp3s using a third-party app like iMovies, first make sure that you have installed that app on your iPhone or iPad. Then, open the app and search for a video that you want to download. Once you’ve found the video, tap on it to open it in fullscreen mode. Next, tap on the three lines in the top left corner of the screen (known as thumbnails) and select “Download MP3.” ..