How can I use my old WiFi router you spread an unsecured WiFi signal I'm picking up on my PC?

My Internet got cut, so I moved my PC to my window so it can pick up any unsecured WiFi networks. There's one I mainly connect to. How can I make my old WiFi router plug into my PC and use Internet Connection Sharing to let my PC send the network to the router, then other PC's in my house can connect to my router to access the network? Is this possible? I'm not to savvy with the access point setting on my router (which is a Belkin Model F7D1301 v1).