Welcome to the forum!
I assume your are testing this plugin
https://plugins.jetbrains.com/plugin/7391-asciidoc. If so, it's nice to preview documents but it does not contain options to directly save them.
You may be more at home with AsciidocFX (
https://www.asciidocfx.com/). Just grab the last version from
https://github.com/asciidocfx/AsciidocFX/releases, and let us know if you have any problem with the installation.