It's a very simple process to setting up the nexmo sms feature with your website
01. On the first step you need to signup with nexmo at : https://dashboard.nexmo.com/sign-up
02. Buy credit / balance and make sure you have enough balance to send sms
03. Login to your nexmo account : https://dashboard.nexmo.com/sign-in
04. Cope the credentials like Key and password of your account as seen below in image
05. Login to your admin panel to go to sms setting page and paste these credentials.
06. Test SMS by sending to your number from settings page if you received the sms you are done with settings.