Problem connecting to network

OK long story short my apt complex has free wifi its pretty fast. I am using it on two PCs. Today I tried to hook up a router to set up a network to be able to share files with them. I wanted to do it hardwired so i wouldnt be sharing my files with everyone.

As soon as I hooked up the router the wireless stayed connected. But the internet didnt work at all. So i take it the hardwired router had a conflict. I unplugged and the internet worked fine.

How do I fix this?

How can i use my wifi adapters for internet and a hardwired router for a local network at the same time?

I also have access to a switch
Would the switch eliminate these problems?

 

Introducing the router gave your computers 2 sources of IP addresses which caused the conflict.
You could use the router but would need to get into the configuration pages and turn off the DHCP on the router. Then it would essentially act as a switch but would have the firewall capability depending on the model.
You could also use the switch or direct connect with a cross-over patch cable.
An option for more security would be to set up a different IP range for the wired connection.
For example, if the wireless IP range is 192.168.1.x, assign the wired connections something in the 192.168.2.x.
(You can find your IP address by START > Run > cmd > ipconfig /all)
(Assigning a static IP - Right click wired Network Connection > Properties > Select Internet Protocol(TCP/IP) > Properties button > Assign IP address)
Hope this helps.