To start representing diagrams a valid model object shall be provided to the component via the schema prop.
A valid model is a plain object having a nodes property set.
The nodes property must be an array of tuples (objects) described by a unique id (it must be unique), a content property (can be a React component) and a coordinates property describing the node position.

Optionally a links property can be set describing links between the nodes, similar to the nodes property it must be an array of valid link describing tuples, a valid link must have an input and an output property.

import Diagram, { createSchema, useSchema } from 'beautiful-react-diagrams';

// the diagram model
const initialSchema = createSchema({
  nodes: [
    { id: 'node-1', content: 'Node 1', coordinates: [250, 60], },
    { id: 'node-2', content: 'Node 2', coordinates: [100, 200], },
    { id: 'node-3', content: 'Node 3', coordinates: [250, 220], },
    { id: 'node-4', content: 'Node 4', coordinates: [400, 200], },
  ],
  links: [
    { input: 'node-1',  output: 'node-2' },
    { input: 'node-1',  output: 'node-3' },
    { input: 'node-1',  output: 'node-4' },
  ]
});

const UncontrolledDiagram = () => {
  // create diagrams schema
  const [schema, { onChange }] = useSchema(initialSchema);

  return (
    <div style={{ height: '22.5rem' }}>
      <Diagram schema={schema} onChange={onChange} />
    </div>
  );
};

<UncontrolledDiagram />