This article explains how to connect an iPhone to a Mac using iCloud, Continuity, and iTunes. Instructions apply to iPhones with iOS 11 and later and Macs with macOS 10.13 and later, unless otherwise noted.
To sync your iPhone and Mac with iCloud, make sure your Mac and iPhone are signed into the same account and have the same sync settings. Then, any changes to data on one device will sync to iCloud and then to the other device, so they’re always in sync.
Sign in to iCloud with your Apple ID. You probably did this when you set up your iPhone and Mac, but follow these steps if you didn't.
Tap your name at the top of the screen.