I've just tried the installation, and that works as described in manual installation, but it cannot be enabled, it shows an error, the error message can be seen in Looking Glass.
After following the troubleshooting hints at
https://micheleg.github.io/dash-to-dock ... greporting and running gnome-shell --replace this is the actual error message:
GNOME Shell-Message: 10:18:08.730: Extension "dash-to-dock@micxgx.gmail.com" had error: TypeError: GObject.registerClass() used with invalid base class (is PopupBaseMenuItem)
As mentioned, you should probably report this upstream at
https://github.com/micheleg/dash-to-dock/issues