Installation of needed tools

You can skip all steps if you already have non-portable Heroic Launcher installed

Comet (needed for leaderboards, multiplayer and achievements)

1. Download latest Comet for your platform from https://github.com/imLinguin/comet/releases/latest.
2. Place binary file at C(or another disk letter where OS is installed):\Program Files\GOG OSS or in case of portable Playnite's version => {PlayniteDir}\GOG OSS (you can select some other directory and set path at advanced settings of plugin if you want).
3. Download dummy-service.zip from website mentioned at first step (you should do that only if you haven't GOG Galaxy installed).
4. Extract dummy service (it can be anywhere, place of extraction isn't important), and launch install-dummy-service.bat (admin rights might be required).

Gogdl (needed for downloading games)

1. Download latest Heroic-gogdl for your platform from https://github.com/Heroic-Games-Launcher/heroic-gogdl/releases/latest.
2. Place binary file at C(or another disk letter where OS is installed):\Program Files\GOG OSS (you can select some other directory and set path at advanced settings of plugin if you want).