Thanks for visiting the Apple Support Communities. From your post, I understand that you would like instruction on purchasing and downloading content from the iTunes Store without signing up for an Apple Music membership. I'm happy to help!
Using the iTunes Store, you're able to purchase and download individual song tracks, or entire albums, and these songs and albums are yours to keep forever. To purchase and download, you first need to make sure you are signed into the iTunes and App Store on your iPhone: Sign in to the iTunes Store on your iPhone, iPad, iPod touch, Mac, PC, or Apple TV - Apple Support .
Once you are signed in, locate and open the iTunes Store app on your iPhone to make the purchases. This is a separate app from the Music app, and in iOS 11, the icon looks like this: . If you cannot locate it by sight, try searching for it: Use Search on your iPhone, iPad, or iPod touch - Apple Support ). Once the iTunes Store app is open, you can use the following information from the iPhone User Guide to purchase and download your music: Purchase, rent, or redeem - iPhone User Guide .