Cannot print to printer on desktop computer using wireless network

Being new to the product I cannot understand messages by advance users. I need step by step instructions.
I’m using COMODO firewall professional

I need to be able to print from my laptop to the printer attached to my desktop computer. I have a wireless router and before COMODO I was able to print with no problem. So is not the operating systems or Network Magic or anything else.

It is quite absurd that once the network is there all the devices attached to the network are not included.