How to share internet on 4 computers

You have a few things here. You can connect 4 monitors to one computer with either one high-end video card or two lower end ones, and you can share internet to 4 computers, what you asking in the post is some odd mix of the two.

If you have a router, just hook up the computers to the router with ethernet cables, reboot the PCs, and you should be set.

If you are asking something else, need more details. If you want 4 users to share one PC, can't do that.