Buy the plugin from Codecanyon by click here. Currently only the WordPress version is available so you need a WordPress website to use this plugin.
Install the plugin like usually by click the Plugins menu and by upload the zip file of the plugin.
From the WordPress admin go to Support > Settings and click the button for start the synchronization. You will be redirected to the Slack login page.
Insert the shortcode |sb] or |sb="chat"] where you want to show the chat or the support desk.