It sounded interesting so I wanted to try it but I couldn't figure out how to actually use it.

It says "We need to know which languages you already know. At least one language needs to be selected as a reference (some symbol) language."

I couldn't figure out how to add that, I also couldn't see that symbol anywhere...

Checked settings, profile, home ("open search" and "create expression" do nothing), create, globe icon thingy... eventually gave up.