Best place to start is checking out this “Creating your first basic node” guide in our docs: Creating Your First Node | Docs
What might help as well is taking a peek at the source code for the Trello node:
We’re currently chipping away at the docs to make them more intuitive and ultimately helpful for users, so please don’t hesitate to share your feedback if you get stuck (and also tap into the awesomely helpful peeps here on the forum).
Happy coding!