Chm is actually a packaged webpage file, so making a chm e-book is roughly divided into two steps: one is to make a webpage, and the other is to package the webpage into chm.
Web pages are usually made by "Soft Scene html Maker" or "hp e-book making software". Web pages are made by buttons of "Previous Page", "Next Page" and "Return to Directory", with various templates and gorgeous effects. Inserting pictures is also very simple. Put the plain text of the e-book and the picture in the same folder, enter the name of the picture in the corresponding position in the text and mark it with a specific symbol (the two softwares are different, which can be understood by reading the help description of the software), and then load the text from the software to output the illustrated web page file. You can also use fckeditor to directly edit the generated web page and add pictures.
After the web page is completed, it can be packaged into chm. There are many packaging softwares, such as easychm and hugechm, which are very simple to use, so I won't say more.
As for software download, you only need Baidu to download it, so don't worry about not downloading it. Basically, it is free, and there is no registration code or anything.