Firewall/printer problem wireless

I've got a wireless network set up in my apartment, with the router connected to cable internet on my desktop. Up until recently, I was able to print a document from my laptop, on the printer connected to the desktop, through the wireless network. But then I installed Trend Micro PC-Cillin anti-virus and firewall, and I can't print anymore. I already know that the problem lies in the firewall, because when I shut it off, the printer works again. But I don't know how to configure the firewall to allow the printer through to the network. I'm not a complete rookie with firewalls...I know how to configure it to allow programs to connect to the internet...I just can't figure out how to allow the printer to connect to the wireless network. Anybody know? Thanks in advance.