General Question about API’s and working with them in Node and JavaScript

I have been in a steep learning curve lately, trying to learn as much as possible about NodeJS and Backend-development in general. I have a project set up and I want to be able to flip some switches on a Website, that then tells the Node-Server what to do, which then makes a call to an API and all the way back to displaying it in the browser. I’ve already worked with promises, but I don’t specifically know how to approach this. Could you maybe provide me with an oversimplified example?

Thank you so much in advance and have a great rest of your day!