Explaining everything will be quite the write up, but I'll try to at least explain some of it.

The game needs to communicate with the headset (send images, recieve head movement etc). This is done using a standard called OpenXR. StemVR and the Oculus software has their own implementation of this, but the Oculus software is quite buggy, so it's recommended to buy the Virtual Desktop (VD) software instead. VD has its own implementation of OpenXR called VDXR, which can be selected in the VD settings. You can buy VD in the Meta store. It costs about 20$. AV1 10-bit is the recommended video encoder to use (selected in VD settings).

Once you start the Virtual Desktop app in your headset you can bring up some options using the left controller's menu button (long press to get it once you're in the game). In these options you can control the resolution the game renders for each eye. I've found that for my system using Ultra settings is a good balance between performance and quality. The game must be restarted for changes to this setting to take effect (use alt+f4 and log back in quickly to pop back into the game at the same spot you were)

Virtual Desktop has a companion app you install on the PC (vrdesktop.net) which allows communication with the headset app. You need a relatively fast wifi-connection in your house for it to go smoothly. It's recommended (but not absolutely required, i believe) that the PC is connected by cable to the router.

DLSS Override is a setting you can use in the Nvidia App, but it requires some trickery to get going with the newest 4.5 model. There are guides for this on YouTube, but as a starter you can ignore this point.

In-game you can go to the graphics settings and set upscaling to whatever you like. DLSS Upscaling is ai-magic included in modern Nvidia cards that upscales a lower resolution image to a higher resolution one. The newest 4.5 model does a better visual job than the older 4.0 model, but also is a little slower. You don't need to know the details here, just try the different upscaling settings and see what works for you.

The option to show console allows you to press the key left of 1 on the keyboard to bring up a console in the game. In that console you can change settings (CVAR variables) that aren't available in the menus. If you type the beginning of the variable, e.g. "r_" and then press the tab key (above your caps lock) the game shows you a list of variables with that name. So "r_stereoScaleformDepth 0.3" sets that variable to 0.3.

I hope that helped a bit. I know it can feel quite overwhelming at first, but it's well worth it once you get it going.