Hi Fabio,
Welcome to Autofocusing!!!
I've updated the Kstars Handbook's chapter on Focus but it hasn't been published yet. From past experience it takes about a week to be published. The older (and of course slightly out of date) version of the handbook is here...
docs.kde.org/trunk5/en/kstars/kstars/index.html
Here is the chapter on Focusing...
docs.kde.org/trunk5/en/kstars/kstars/tool-ekos.html#ekos-focus
I'll let you know when the new version of the Handbook is published. However, although the links are slightly out of date they contain quite a bit of information that is still relevant.
In terms of getting started I would recommend Focus Advisor (which it looks like you've found) which is a new feature which is intended to help navigate the options for new users. Although FA will default the majority of options automatically there are 2 things you need to do work on yourself...
1. Backlash
a). The ZWO EAF has backlash so you will need to measure it. There are many ways to do this. I have a refractor with draw tube so what I do is put a piece of tissue paper on the draw tube focus knob (that the EAF will rotate). Move the focuser out by a large amount, say 1000 ticks. Then, in increments of 10 ticks move the focuser in, whilst watching the tissue paper. If it moves on say, the 9th movement then your backlash is somewhere between 80 and 90 ticks. Do it 3 times and take the largest of the 3 measures, lets call it 100.
b). For the ASI EAF I would recommend a backlash strategy of using "AF Overscan". In order to use it set the Driver Backlash field to zero, and the AF Overscan field > backlash value you measured in a) above. Set it to 150, for example.
2. Step Size
The step size needs to be a sensible value for your setup in order for Autofocus to work. If its too small then the focuser won't move enough between steps to have an effect on star size; if its too big you'll move so far out of focus that you'll lose all the stars. So as a rule of thumb if you start approximately at focus, then by moving 5 steps outwards, you should have a star HFR approximately 2 or 3 times what it is at focus (if you have a refractor 3x is fine; if you have a telescope with a central obstruction then 2x is probably OK - 3x may give you donut shaped stars that may cause focus problems).
So you could try experimenting with Step Size to get the above rule of thumb to work.
Another option is to use the Critical Focus Zone tab to work out the CFZ for your setup. This doesn't need to be exact. Use say the Classic algorithm. The 1 piece of work to do here is to measure the step size in microns for your equipment. The tooltip for Step Size on the CFZ tab describes a way to do this which is to move the focuser from all the way out to all the way in (and note how many ticks its moved). Measure how far the draw tube moves with callipers or a ruler. So you have x ticks moves y mm, so convert this to 1 tick = z microns. Enter this into Step Size in CFZ tab. The other parameters are defaulted from the Optical Train for your setup. Use a wavelength of say 500nm.
The Final CFZ in ticks can be used as a starting step size for Focus.
Focus Advisor can be used to update all the other parameters - as you've found.
This should get you started with focus. You'll no doubt get better results by tweaking some parameters as you learn more.
To use Autofocus, manually get roughly in Focus with a broadband filter (e.g. Luminance) and hit Autofocus.
Let me know how it goes. I'd like to update Focus Advisor with user feedback so I'm very interested to hear your comments.