Hello you have to install ClamAV onto the server in order to use it. The CLAMAVSETUP.EXE is the right one if you use an Windows-Server. Login as Administrator and start the installation process. If you are using an Linux-Server you can install ClamAV with your packetmanager e.g. apt-get clamav. If you have no administration-access to the server e.g. you only have an hosting-account and no root-server, you shold contact your hostingprovider asking them to intall ClamAV and telling you the Path to the executable to use in moodle.