• Open the Particle Web IDE at https://build.particle.io/build/
• Select the "Libraries" tab in the right hand side, which looks like: 

• Search the library you want to use! Note: it's possible that the library you would like to use isn't available in the Libraries tab on the Web IDE. In this case, consider using the Particle Workbench on VSCode

To read more: https://docs.particle.io/getting-started/device-os/firmware-libraries/