how can i add computeror printer to a network

If the printer has a network interface wired or wireless, then connect it as you would any other network device. If you have DHCP services on the network, it will get an IP address. If you don't have a LCD panel on the printer to see the IP, you should be able to print out a test page of some sort to print the config.

If it's not a network printer, you can connect it via USB or parallel cable ( for really old printers) and share the printer over the network via the OS sharing process

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