How do I set up my modem-router combo to connect to the internet automatically?

I’m helping out a neighbor who’s sitting on an old Kasda DSL Router. He wants to know if there’s any way to set it up so it just connects to the internet automatically—you know, without having to dive into the network settings every single time... When I was a kid, we had a setup like this at home, but I never really grasped how they pulled it off, and honestly, I can't figure it out myself now. I’m definitely no network admin guru, and I have no clue where to hunt down the configuration info. Any advice?

I don't think you can learn all of this through a forum... especially not in ten minutes...
My internet setup looks like this:

A standard
..using two phone lines
that connect to a modem, which then connects to a Router, and from there, one or more computers connect via Wi-Fi or an Ethernet cable. You need a device—or integrated hardware—plus the necessary drivers and software.
There are also Modem-router combos that handle everything at once. They have a built-in CPU, essentially making them small computers with limited memory.
To get a single Router running properly, you have to configure one to three different passwords. And so on...
Nobody taught me any of this; nothing in school helped, even though I am an Electrical engineer. Back then, the internet didn't exist. We took our first steps using an Acoustic coupler, and then moved on to the very first modems. It was a long time before the internet became a reality. We were the pioneers of digital communication.
We learned the mechanics gradually, figuring things out just as the era of the internet arrived.
Who else reading this remembers those early modems? Perhaps you recall the best protocol: Z-Modem?
It was fast, and it verified if the receiver understood every block perfectly.

In short, I've already told you quite a bit. Yet, here you are, searching the web to learn what a modem is, what a router does, and how they connect and configure. Every router has its own unique software and interface.

Good luck.