You can install Formie via the plugin store, or through Composer.
To install Formie, navigate to the Plugin Store section of your Craft control panel, search for Formie, 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:
cd /path/to/project
Then tell Composer to require the plugin, and Craft to install it:
composer require verbb/formie && php craft plugin/install formie
You can try Formie in a development environment for as long as you like. Once your site goes live, you are required to purchase a license for the plugin.
For more information, see Craft's Commercial Plugin Licensing (opens new window).