Use your internet account with other macOS apps
When you log in to some websites for the first time, Safari asks if you want to use your account with apps such as Mail, Messages, and Calendar.
To have macOS set up your apps with this account, click one of these buttons:
Add Account: Choose which apps to use the account with, and open them now. (This button is shown for only some accounts.)
Allow: Let other apps use this account. (This button is shown for only some accounts.)
Not Now: Add your account to apps later.
No matter which button you click now, you can use the Internet Accounts pane of System Preferences later to add internet accounts, see accounts you already added, and choose which apps to use each account with. You don’t need to set up your account separately in each app.