1. You'll need to install the following:
a)
Sigil 0.9.1.3
b)
Amazon Kindle Previewer 3.30.
c)
The KindleGen plugin (only if haven't already installed it)
When asked, accept whatever installation folder the installer suggests.
(If Sigil or Kindle Previewer is already installed, the installer will automatically update the existing version.)
After the installation, open an epub with Sigil and select
Plugins > Output > KindleGen. This'll display a settings dialog box, which you can use to customize settings such as the compression value. (The plugin will remember this value.)