Now we're starting to bring the existing accounts together. In the series of screenshots below, you will invite your dummy account in Google+ (using the Dummy account's / Youtube account's email address) as the invitee manager.

This will generate an email to the dummy account (which you will now have to retrieve). Once you log in to the email account of the Dummy account you should see an email invite that looks like this one - so click the link in the email to accept the invite.