To connect your printer via 123.hp.com login, start by connecting it to your network and powering it on. Then, visit 123.hp.com and select your printer model. Follow the on-screen instructions to download and install the appropriate drivers. After installation, open a web browser and navigate to 123.hp.com/login to access your printer's settings. Enter your credentials and configure the printer as desired. Finally, test print to ensure everything is functioning correctly.