How to set a Circle CI environment variable for a project? I've set the environment variable with a "context" (I have no idea if thats the right place - it's really confusing!)

None the less, it's now doing a build - and I don't see the environment variables set (I'm using the SSH build to inspect the vars with getenv).

Why is it not being picked up? Am I meant to set an environment variable by some other means rather than a "context"?
https://circleci.com/docs/2.0/env-vars/#setting-an-environment-variable-in-a-project

Seems "contexts" can be used but must then also be set to "reference" the context in the build yaml config file.

Instead to set a environment variable for a project:
Jobs > Cog / gear icon of a project > Build settings > Environment variable