How are drivers installed in Linux (in KDE systems) in general?
First off all, KDE has little to do with "drivers" the method of install.
A few distros supply some gui tools to ease the way "drivers" are installed.
Next, the more correct term would be "Kernel Loadable Module" or KLM for short. This is one of the differences between linux systems and windbloze.
KLM's interface with the kernel, linux itself. There is a second way, and that is to compile your kernel, and add the hardware support into the kernel. ( Not recommended for a noob ).
To load a KLM, once it is installed on the hard drive, you use the command 'modprobe klmname'. The system will look for the klmname, and try to load it into the kernel. If successful, linux responds without any messages, so no news is good news.
Once the module is loaded, configuration amy be needed, say for example this is a KLM for an ehternet card. You would have to use commands, or edit files to configure the device. Using ethernet as an example, you can configure the ethernet interface with the commamd ifconfig. Usually you would want to edit some files, so the config is not lost on the next boot.
There is a great deal of work going on for distros to detect the hardware on install. If your hardware gets detected, usually the code will set the system up to load the KLM without any intervention by the user. This is an ongoing work, and probably will never be finished, since new hardware is always being released. This is one area distros differ. Hardware detection is better on some compared to others.
I'm looking for a beginners guide aimed at Windows users.
I would suggest you look at the board for your distro. You didn't state which one. Most of them have How-tos and a hardware support area. Such a document would be very difficult to write and keep general.
Hope this helps.