Good afternoon BupGong,
Welcome to the Apple Support Communities!
Congratulations on the purchase of your iPhone 8! Are you receiving pop-ups regarding the Apple Music Membership trial, or are you seeing this when you open the Music app?
In the Settings app, tap Music. If there is a green button beside "Show Apple Music," tap the green button to turn this feature off. In the Music settings, "iCloud Music Library" will be off as it is a feature of the Apple Music Membership as well.
While you are on this screen, you can decide whether or not to allow Cellular Data for music downloads. Press the Home button when you are done to return to your Home screen.
I'll include the iPhone User Guide for iOS 11 below to help you get started with your new iPhone. To get back to the Table of Contents from any page, tap the icon that looks like a bulleted list at the upper-left corner of the page.
iPhone User Guide - iPhone 8
All the best to you in 2018!