Martin,
The basics are the same between AS2! and AS3!
https://www.autostakkert.com/wp/guides/
The "Open " box will allow you to load an AVI or SER video file...
Image Stabilization - Select "surface" for solar/ lunar and "Planet" for planets (!)
Quality Estimator - leave as default, set "Local" to stack on an object, ("Global" to stack on the whole frame -never used it..)
Then press "Analyse" - it will go through your video file, find the best quality frame and then sort all the others to produce a green curve on the graph.
This gives you some idea about the quality/ quantity of "good" frames worth stacking to an image.
(Each line is 25% - ie top left hand "box" gives the best 25% images, you can estimate how many frames -10%, 15% or 25%. Use this to set the Stack options...
Output normally to a tiff file, # of frames (or percentage) as per the graph..
If you select "sharpened" this applies wavelets (similar to Registax) and outputs two images, one "as stacked" and one as "sharpened" so you can select the un-sharpened image to process yourself in Registax if you thank you can improve on the AS3! outcome.
I don't use "drizzle" but some say it can help....
Go to the image screen - set the target area (Ctl+left click) then select the Alignment points - I use the "AP grid" - you can try various AP sizes - 24/48/104 etc - I use the 24 or 48 the most with the ASI 1600.
Press "Place AP grid" and you'll see an array of grids on your images...
Then finally, press "Stack" and wait until the message area at the bottom shows "done"
The trick if any is to select the best quality frames and the AP sizing to give the best stack result.
You'll find the processed images in an "AS" folder within the original video folder.
Hope that helps.