Don't actually drag anything. You are selecting a sub-menu under the Apple icon which on older systems was called System Preferences. Under System Preferences you are then selecting the iCloud Preferences item. That will open a window to iCloud settings for that particular user account on the computer (a family might have several computer accounts) and you can see if there's one set up in there. If there is, we can proceed with steps for recovering lost account information. If there isn't, your friend can create an APple ID/Account and setup iCloud for the account on the computer. I strongly suspect there would be an ID set there since you need one to do almost anything such as updating the system or applications.
This document tells you the various ways you can try to discover your forgotten Apple ID --> If you forgot your Apple ID email address or phone number - Apple Support Note that typically this is an email address you use.
This document outlines what to do If you forgot your Apple ID password --> If you forgot your Apple ID password - Apple Support
or go directly to this link --> http://iforgot.apple.com/
If you still need help:
Contact Apple for help with Apple ID account security "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues." Click here --> Contact Apple for help with Apple ID account security - Apple Support