To add your authorized IP, please go to https://highproxies.com/billing/myproxies.php
(Login to https://highproxies.com and go to Services -> My Proxies).
Add your current computer (or VPS) IP address in one of IP1/IP2/IP3 boxes and click on the "SETUP" button.
You can add up to 3 authorized IP addresses/devices (IP1/IP2/IP3 boxes).