Hi @santoshpoudel713, hope you are doing well.
First of all, I’d like to recommend you to check the plugin’s Live Demo and Demo Editor pages, there you can find the description of the plugin, short setup guide, and demo page editor (exemplary use case setup).
Before using the plugin in your app it is needed to create a new account on the Mailboxlayer site. From there you can retrieve the API key that you can later add to the plugin settings (it is a required step).
Please let me know if there is anything else I can help you with.
Regards,
Zeroqode Support Team