Troubleshooting

I can't add a library to my schematic

Is your schematic part of a project or a "free document"? It's probably the later, so you first need to create a project and then drag your schematic file into the project (in Altium, not in the Windows File Explorer). See https://github.com/BEAMS-EE/ELECH402/wiki/Schematics#create-a-new-schematic