It only works with the desktop version, not the android app.

If you use the Graphical UI, go to Menu Bar > Tools > Plugins, enable the NWC plugin, then go to Menu Bar > Wallet > Nostr Wallet Connect, create a new connection, scan the QR code with your nostr client and you should be ready to go. You need an active lightning channel too and Electrum needs to be running while you want to send zaps.

You can also run it as headless daemon on a server through the CLI.

See the docs here https://electrum.readthedocs.io/en/latest/index.html