To install your HP printer using 123.hp.com/setup, first, ensure your printer is powered on and connected to your Wi-Fi network. Next, open a web browser and visit 123.hp.com/setup. Enter your printer model to download the necessary software for your operating system. Once the download is complete, run the installer and follow the on-screen prompts to complete the setup. The software will guide you through connecting the printer to your network and installing the required drivers. After installation, your printer should be ready for use. Visit 123.hp.com/setup anytime for troubleshooting and support.