Download new ProcessWire modules from the official website. Once downloaded, follow these steps:
Place the .module file in the site/modules/ directory. If the module contains more than one file (for example, supporting .css or .js files), a new directory should be created for the module under the site/modules directory with the same name as the module. For instance, the AdminBar module and supporting files would be placed in the site/modules/AdminBar/ directory.
Log in to the ProcessWire administration dashboard.
Select the “Modules” tab.
Click the “Check for new modules” button.
Click the “Install” button next to the modules to be installed.