Exchange 2010 and Barracuda 300

We have a new Barracuda 300 spam/virus device and we need to start using it but I am not clear on how to get Exchange to use it.

We currently use Symantec Cloud as our spam/virus filter so our MX record points to them. 

Any help configuring Exchange 2010 would be greatly appreciated.

I know we also need to make some firewall changes and will research that as well.

Thanks in advance.