Struggling with where to make changes fo Bunny CDN

invalid@example.com (Vlasta), Vlasta
Mon, 12 Jan 2026 11:41:34 +0000
Server configuration and hosting

I know I have to add the appropriate lines in a config file as per below... BUT which file?

my /src file has the following entries. So my "guess" it is XF.php - right?

I am running:-

Xenforo 2.3.7
PHP version 8.3.6
MySQL version 8.0.44 (8.0.44-0ubuntu0.24.04.2)
Server...