To purchase WHOIS Privacy, you will need to do the following:
Log into your 123-reg control panel.
In the Domain names section, click on the Buy link below WHOIS privacy.
Select the domain name that you want to apply the WHOIS Privacy to and the number of years you want to purchase it for.
Click on the add WHOIS privacy button.
Follow the on screen payment instructions.
Please note: You will receive a WHOIS Privacy welcome email that will explain step by step how to activate the WHOIS Privacy on your domain name.