where is varnish configuration file?

Hello to all.
I have a file, a cronjob heavy enough.
Varnish gives me a 503 error.

I found an online solution
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varnish 503 can be fixed by steps below:

Increase the connect_timeout, .first_byte_timeout and .between_bytes_timeout you in setting backend:
backend default {
   .host = "www.xxx.com";
   .connect_timeout = 5s;
   .first_byte_timeout = 10s;
   .between_bytes_timeout = 10s;
}
Increase the parameter to 8192 When start varnish.
varnishd [options] http_resp_hdr_len = 8192
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But where is varnish configuration files in centos webpanel? Where I add these lines?

/etc/varnish/

Which file?

In which file I add the lines of code?

Found ... is backends.vlc