The linked guide refers to someone who already has Ubuntu installed, so you wouldn't be able to find the settings if you have yet to install Ubuntu.
To proceed with the install and avoid the black screen and error message, BEFORE you try to select the option "Try Ubuntu..." or "Install Ubuntu", pres F6 to bring up Other Options and then use the keyboard to select nomodeset and press Enter or Space Bar to select the option, then try running install or "Trying Ubunutu".
If that still does not resolve the issue, do the same steps again but this time after selecting nomodeset hit F6 again and then also select acpi=off to see if that works. This setting is not necessarily ideal for laptops because of its role in power management but if it can get you through the install, then any updates Ubuntu finds should hopefully address that. But you may want, either before attempting the install or after you've had success with the install (hopefully), to try checking if your laptop has a BIOS update since you did mention it was an older laptop (though "older" can be subjective).
Once it is installed, you can follow the guide you linked by entering Ubuntu in recovery mode if the issue persists following installation or following a BIOS update. And, in case it wasn't something you already checked, try changing system to UEFI mode if it's not in UEFI mode already. I just wouldn't recommend trying to do the grub configurations through Windows, in case that's what you had meant when you tried searching for it and you were using Windows.
