How to install a plugin?

Can anyone explain how plugins work?

I tend to think of a plugin that is easy and seamless to install, say in a web browser, but from looking at people’s plugins on github it seems like I would actually have to manually insert the plugin into the source and compile.

The plugin infrastructure is still under development. Packaging of plugins is a manual process at the moment, as is the installation. Whether end users have to compile the plugin or not is up to the developer, it is possible to distribute prebuilt binaries so end users don’t have to compile the plugin themselves.