Congrats on your purchase!  In order to get Internet on your new computer, you don’t have to do much!

If you use a router, just connect the computer to your WiFi (wireless) network.  Most new computers ask you to do this the first time you start them up.
If you do NOT have a router, just plug your Ethernet cable that was in your old computer to the new one.  Turn the computer on, and you should have Internet!