WHMCS system URL

Hello,

I am using onehost theme. Please check the screenshot. This is what we receive while a support ticket is created. But when we the click the link received in email, it is going nowhere.

2)When I click the client area from Admin.It is going to default template link here. https://red-proxy.net/support/clientarea.php
How to change this to theme?

3) I contacted theme author he asked me to contact whmcs. Whmcs support asked to update the WHMCS System URL here : https://red-proxy.net/support/admin/configgeneral.php

This is what I am seeing in the configgeneral.php. https://i.imgur.com/TyYft7Q.jpg

Where I need to update the whmcs system URL?

Can anyone please guide.

Thank You