1. Add a language in the block "Language settings for the field names in the form" on the plugin settings page.
2. Mark the checkbox (if it's not marked yet) in the block "Change the names of the contact form fields and error messages", choose the necessary tab, click the twistie to expand the list of the fields and fill in the fields. Choose the necessary tab in the block "Action after email is sent" as well and fill in the field. Save the changes.
3. You will see the shortcode under the tab with the necessary language. Please paste that shortcode to the page or post.