In case you don't want to build the frontend yourself, e.g. you don't want to install npm, gulp and tons of JS dependencies, you can find the prebuilt UI here.
In your birdseye application directory (e.g. /opt/ecix/birdseye/)
just type
./bin/fetch_ui_dist
This is usually done by the startup script start_uwsgi.
However, you can disable auto downloading by setting autodownload_ui = false
in your /etc/birdseye/birdseye.conf