FreeBSD offers two versions of Varnish pre-packaged:
pkg install varnish6
or, if for some reason you want the older version:
pkg install varnish4
The FreeBSD packages are built out of the “ports” tree, and you can install varnish directly from ports if you prefer, for instance to get a newer version of Varnish than the current set of prebuilt packages provide:
cd /usr/ports/www/varnish6 make all install clean
Copyright © 2006 Verdens Gang AS
Copyright © 2006–2020 Varnish Software AS
Licensed under the BSD-2-Clause License.
https://varnish-cache.org/docs/6.5/installation/install_freebsd.html