iCloud is a bigger deal than you think. In this case, Apple allows its users to use iCloud password to unlock their Mac. Normally, to keep your Mac secure, you will need to already have permission to access your Mac’s settings.
By default, if you have set up iCloud on your Mac, you can use your iCloud password to login to your Mac. However, if for some reasons that you want to re-activate the options, read on.
How to unlock Mac using iCloud: System Preferences
Step 1: To change your login options, you will need to have access to system preferences. To do this, you can click the Apple logo in the upper – left corner of your screen, and select System Preferences.
Step 2: Once you have clicked System Preferences, a pop-up window will appear, and click on the Users & Groups, and select the Mac account that you are currently logged into from the left side. Note that this account will be associated with your Apple ID/iCloud to unlock your Mac.
Step 3: Once it is done, click the “Change Password” next to the users name to proceed. You will be presented with the option to either change the password for the Mac account you are currently logged into or use iCloud password to unlock your Mac.
Step 4: Choose “Use iCloud password”, and type in your old password, iCloud account (your Apple ID) and iCloud password. Once it is done, choose “Use iCloud Password” to set this as a login for your Mac.
From now on, you can use the Apple ID and iCloud account to login to your Mac every time you are at login screen. This unlocking method can be useful, as it reduces the total number of logins and passwords you need to remember. If you happen to lose or forget your Apple ID password and login details, you will need to recover it.