Possible that the links to the docs just aren't in reasonable places, but it is documented a lot.

https://aerogear.org/docs/unifiedpush/ups_userguide/index/#_sending_a_push_notification_from_code
https://aerogear.org/docs/specs/aerogear-unifiedpush-nodejs-client/
https://www.npmjs.com/package/unifiedpush-node-sender

In UPS there is also these are in the console to guide you as well :