To enable languages: Settings > Languages & Layouts. It might just take a bit of usage for all the corrections and suggestions to kick in.

To switch languages or keyboards: Long press the space bar.

If you haven't enabled number row in Preferences, just long press Q to get 1.

I'd also recommend:
- Downloading the emoji dictionary 👍
- Having a root around in settings
- Reading up on the "hidden" functionality
The power of Heliboard, and the reason it got me to abandon Gboard where others failed, is in the last two.
Hope that helps - I am still new to Heliboard (but I am already sold on it) and a power user might have better insight but that might be enough to get you going. If not, ask away.