The best way to install FreezyBee/Mailgun is using Composer:
$ composer require freezy-bee/mailgun
With Nette 2.3
and newer, you can enable the extension using your neon config.
extensions:
mailgun: FreezyBee\Mailgun\DI\MailgunExtension
mailgun:
domain: example.com # required
key: key # required
autowired: true # default false - if you set it true -> it force autowired all IMailer interfaces to Mailgun