Download/install from: https://www.clamav.net/downloads
Open terminal
One time:
sudo cp /usr/local/clamav/etc/freshclam.conf.sample /usr/local/clamav/etc/freshclam.conf
sudo /usr/bin/sed -i '' 's/Example/# Example/' /usr/local/clamav/etc/freshclam.conf
sudo cp /usr/local/clamav/etc/clamd.conf.sample /usr/local/clamav/etc/clamd.conf
sudo /usr/bin/sed -i '' 's/Example/# Example/' /usr/local/clamav/etc/clamd.conf