In a similar manner as Alpha Zero, Leela is growing by playing games with people and with itself (mostly). It is already a strong expert or low rated master at this point.

Youtube chess (masters) like ChessNetwork and Kingcrusher have videos of them playing it.

- https://www.youtube.com/watch?v=Z_-qtuuhLnI - https://www.youtube.com/watch?v=gLvxGXNLs-0

You can help make it stronger by donating your CPU/GPU cycles!