You can use Module as a design system library in other files or projects. With the Free version of Figma, you can publish styles but not components. To publish components, you should have a paid Figma plan.
After adding the Figma file to your project folder, open the file and Publish styles and components in the toolbar.
Now you can connect and use Module library in any file. Go to the project file and open Libraries menu in the left sidebar to enable Module. Done.
Note: You can also use all Module features without a paid plan, just create a new page inside Module file and design there.