1. Open a web browser and go to the Apple website at www.apple.com.
2. In the top right corner of the page, click on the "Support" link.
3. On the Support page, scroll down to the "Downloads" section and click on the "iTunes" link.
4. On the iTunes download page, click on the "Download" button.
5. The iTunes installer will be downloaded to your computer.
6. Once the installer has been downloaded, double-click on it to start the installation process.
7. Follow the on-screen instructions to complete the installation.
Note: If you are using a Mac, iTunes is already pre-installed on your computer and does not need to be downloaded.