just got an rt-ax86u, how do i even set it up? my modem is already connected to my old router.

Diagnosis: You need to swap out your old router with the new one. It's a straightforward process.

Fix: Follow these steps for a wired setup:

1. Unplug the power cable from your modem. If it has a battery backup, remove that battery too.
2. Disconnect your old router. Connect your modem to the WAN (Internet) port on your new RT-AX86U using the bundled network cable.
3. Plug your modem back in and power it on. Wait for its connection lights to stabilize.
4. Plug your RT-AX86U into a power outlet and press the Power button.
5. Connect your computer to one of the router's LAN ports (1-4) with another network cable.
6. Open a web browser. The setup page should launch automatically. If it doesn't, type http://router.asus.com into the address bar.
7. Follow the on-screen instructions to set a router password and configure your Wi-Fi networks.

If that didn't work: For a DSL connection, you'll need the username and password from your Internet Service Provider (ISP) to complete the router configuration in the web interface.