Windows:
1. Go to the Apple website and click on the "Download iTunes" button.
2. Once the download is complete, double-click on the installation file to start the installation process.
3. Follow the on-screen instructions to complete the installation.
Mac:
1. iTunes comes pre-installed on all Macs. If you need to reinstall it, you can find it in the Applications folder.
2. Double-click on the iTunes icon to launch the application.
3. If you have an existing Apple ID, enter it. If you don't have an Apple ID, you can create one for free.
4. Click on the "Update" button to install the latest version of iTunes.