Open a text editor.
Navigate to https://github.com/pceiley/scripts/blob/05a557297594631e06581d3b546d9119c2f4a46c/clearlinux/install_hplip_plugin.sh in your web browser.
Copy the text for the script and paste it into your text editor.
Save the file somewhere in your home directory and give it a name. For this example I’ll use the location ~/scripts/install_hplip_plugin.sh
Open a terminal.
Navigate to the directory with the script eg:
Change the permissions on the script to make it executable:
chmod +x install_hplip_plugin.sh
Run the script with root priveledges:
Open Settings and navigate to Devices -> Printers.
Click the Unlock button at the top of the screen and type your password.
Click the Add button to add a printer.
Hopefully it will detect your printer automatically, if not it will let you type the IP address of the printer in the dialogue.