When somebody adds you as a contact and you do not have the Trusted Contacts app installed, you will get notifications at the email address or phone number that was chosen by the person that added you. You can ask the person to remove you as a contact and then add you again using a different email address or phone number.
If you are added as a contact with an email address that is not associated with a Google Account or with your phone number, you will be sent a link that will allow you to choose where you want to be notified. You can choose between your Google Account email address, or another email address or phone number that was previously associated with Trusted Contacts. Note that the chosen email address or phone number will be used for all location share notifications from any Trusted Contacts user.