A 0install application is distributed using a feed file. A feed is an XML file that tells 0install how to run the application, and which versions are available. The feed file is normally published on the web; the URL of the feed is the unique identifier of the application.
For example, Visual Studio Code is available via 0install. It has this feed file: https://apps.0install.net/gui/vs-code.xml
To get a 0install application:
Find a program you want to run on the web:
Either launch it directly:
0install run https://apps.0install.net/gui/vs-code.xml
Or create a menu entry or command-line alias to launch it later.