I have a router and one computer is there so thats fine. Then from that router I have taken an ethernet cable at the back of the house (in the office) about 20 meter away. Now there I want to use two computers. Can I get a splitter or something else to connect that ethernet cable to and use second computer to that.
when it turns up simply plug the long cable from the router into any port on the switch and then plug the two computers into any other port on the switch (it really doesn't matter where you plug any thing into it)
Don't forget you will need a couple more Ethernet cables of the right length to connect each of the two computers to the switch though.