How to call view controller from Main App

Just starting my journey in Swift and was following a vague YouTube tutorial. I'm having an issue calling the ContentView from the Main App. Any help is greatly appreciated along with any recommended material for learning the Swift language.

(I come from a Salesforce Developer background so I'm semi fluent in Java, HTML, SOQL, and Javascript)

Main App:

import SwiftUI

@main
struct RoundBarrelSocietyApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

ContentView:

import SwiftUI

import UIKit

class ViewController: UIViewController {
    private let imageView: UIImageView = {
        let imageView = UIImageView()
        imageView.contentMode = .scaleAspectFill
        imageView.backgroundColor = .white
        return imageView
    }()
    
    private let button: UIButton = {
        let button = UIButton()
        button.backgroundColor = .white
        button.setTitle("Random Photo", for: .normal)
        button.setTitleColor(.black, for: .normal)
        return button
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBlue
        view.addSubview(imageView)
        imageView.frame = CGRect(x: 0, y: 0, width: 300, height: 300)
        imageView.center = view.center
        
        getRandomPhoto()
        
        button.addTarget(self, action: #selector(didTapButton),
                         for: .touchUpInside)
    }
    
    @objc func didTapButton() {
        getRandomPhoto()
    }
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        view.addSubview(button)
        
        button.frame = CGRect(
            x: 30,
            y: view.frame.size.height-150-view.safeAreaInsets.bottom,
            width: view.frame.size.width-60,
            height: 55
        )
    }
    
    func getRandomPhoto(){
        let urlString =
            "https://source.unsplash.com/random/600x600"
        let url = URL(string: urlString)!
        guard let data = try? Data(contentsOf: url) else {
            return
        }
        imageView.image = UIImage(data: data)
    }
}