Use following Steps To get API & Sample Code:

1) Login to bulk SMS portal.

2) Inside Login left side in Menu below of delivery report option you can get API option click on that.

Bulk SMS API section

3) After that, you can get there your auth key and click on API documentation option for sample code.

Secure

4) After clicking the API Documentation option you can get sample code on the top menu bar you can click on that & take your code and try to integrate.

Bulk SMS API Sample Code

Bulk SMS API for developers