Set up a second iCloud account on Mac
You can add a second iCloud account in Internet Accounts preferences to use with Mail, Contacts, Calendars, Reminders and Messages. You can use only your primary iCloud account for other iCloud features, such as iCloud Drive, Photos, Safari, Notes, iCloud Keychain and Find My Mac.
Add a second iCloud account
On your Mac, choose Apple menu > System Preferences, then click Internet Accounts.
Click the Add button , then click iCloud.
Enter your second Apple ID (or click Create Apple ID), enter the password, then click Sign In.
Change account details
On your Mac, choose Apple menu > System Preferences, then click Internet Accounts.
Select your second iCloud account on the left, then click Details to view the Apple ID used for this iCloud account, and to change the account description shown in Internet Accounts preferences.
Turn features on or off
On your Mac, choose Apple menu > System Preferences, then click Internet Accounts.
Select your second iCloud account on the left, then select each feature you want to use, and deselect any feature you don’t want to use.
If you select the Contacts feature while your Contacts app is synced with Google Contacts, Google syncing is turned off. You should keep it turned off while using iCloud for your contacts.
Manage iCloud storage
On your Mac, choose Apple menu > System Preferences, then click Internet Accounts.
Select your second iCloud account on the left, then click Manage. See Manage iCloud storage.
Remove a second iCloud account
On your Mac, choose Apple menu > System Preferences, then click Internet Accounts.
Select your second iCloud account on the left, then click the Remove button .
If your Mac is set up for iCloud Keychain when you remove a second iCloud account, you’re asked whether to remove the account from your other Mac computers set up for iCloud Keychain, or just turn off all the account features on this Mac.
For more information about using iCloud features in macOS apps, such as Mail or Contacts, open the app, choose Help > [app] Help, then search for iCloud.