Head to a local computer store and ask for a simple wired router or switch. You can find good cheap ones for around $25-$35 that are more than fit for home use, sharing a broadband connection and making a small home network to share files.
The port quantity can vary from 4 to 10 depending on the brand and price, make sure it is a 10/100 mbps one for faster transfers between computers and better network sharing. They usually don't require any software or configuration.
Make sure to have the proper firewall and antivirus software too for keeping the network secure, not that anyone will steal your bandwidth on a wired network.
It is always better to keep the computers protected against viruses and hackers which could harm your data. You can also contact the company that provides support for your wireless router and have them guide you on how to set permission only for certain computers to access your wireless network.
I have a wired network myself, not that the computers at home are very far from each other but saves me the time to change the access settings every now and then to keep it secure.
(Yes, I know that a determined hacker can break into a home wireless network if they really put their hearts into it, but they usually pick on easier prey who have their wireless network fully open).