If you wish to connect your current router, you can start by reading this article: https://support.nordvpn.com/hc/en-us/articles/213722849-Setting-up-a-router-with-NordVPN
We have many articles for various router setups here: https://support.nordvpn.com/hc/en-us/sections/201889785-Routers-NAS
If your router is not compatible, we would recommend you to purchase a DD-WRT or Tomato compatible router and set it up with NordVPN. You can also purchase an already set up router. You can find all the required information on this page.