Problems with installing Box2D plugin

Hey all, I've veen wanting to try the above plugin, but I can't get it to happen. They advise to use the AssetLib in Godot itself, but the plugin doesn't appear there when I search for it. The browser version of the AssetLib does find it, but the download link gives a 404. I've then downloaded the latest release directly from github, but it does not contain the necessary "addons" directory which is needed for manual installation.

I'm kind of stumped. I didn't expect such a popular plugin to be so hard to install...

Any suggestions?