How to invoke methods

Get a reference to the treeModel attribute to access the API.
For example:

<tree-root #tree [nodes]="nodes"></tree-root>

  <button (click)="tree.treeModel.focusNextNode()">Next</button>
  <button (click)="tree.treeModel.focusPreviousNode()">Prev</button>

Or using a ViewChild:

import { TreeComponent, TreeModel, TreeNode } from 'angular-tree-component';

class MyComponent {
  @ViewChild('tree') treeComponent: TreeComponent;

  ngAfterInit() {
    const treeModel:TreeModel = this.treeComponent.treeModel;
    const firstNode:TreeNode = treeModel.getFirstRoot();
    
    firstNode.setActiveAndVisible();
  }
}

Complete API

You can find the complete API of the TreeModel here: