You can install Many to Many via the plugin store, or through Composer.
To install Many to Many, navigate to the Plugin Store section of your Craft control panel, search for
Many to Many, and click the Try button.
You can also add the package to your project using Composer and the command line.
Open your terminal and go to your Craft project:
Then tell Composer to require the plugin, and Craft to install it:
composer require verbb/many-to-many && php craft plugin/install many-to-many