Recursively add child nodes to TreeView C#

I didn't think this would be that hard to do but I have been stuck on this for the last 45 minutes or so. I am trying to make a recursive function that finds files in a directory and add them to the TreeView. This is my method so far:

        private void RecursiveAddToTree(string path, TreeNode parent)
        {
            var directories = Directory.GetDirectories(path);
            var files = Directory.GetFiles(path);
            foreach (var directory in directories)
            {
                var node = new TreeNode(getItemOrDirectoryName(directory)) {ImageIndex = 0, SelectedImageIndex = 1};
                //this is where I need to add the child node to the parent node
                RecursiveAddToTree(directory,node);
            }
            
            foreach (var file in files)
            {
                var node = new TreeNode(getItemOrDirectoryName(file)) {ImageIndex = 0, SelectedImageIndex = 0};
                //this is where I need to add the child node to the parent node
            }
        }
    

I'm looking for a way to add a child node to a parent node given the parent node, but I can't seem to figure out how to do that.