Typically, you'll need to put the folder in /var/www on your server - this is normally where Apache serves content from. That said, you'll need to check the Apache configuration as it can vary from system to system.

You can also change Apache's configuration to serve content from a totally different directory (e.g. /srv/www) as long as the filesystem permissions allow Apache read access.

Apache will also need write access to wherever you configure it to place the cache files - I've set the default to be /tmp but this is cleared after every reboot, so it may not be appropriate in all cases.