Use following steps & secure your API :
1) Login in our SMS portal For Login Process visit here.
2) Inside login Left side below corner beside of setting you can get API option click on that.
3) You can get there Security Tab clicks on that. Select there Enable Option. Add there your IP Address & white list it.
4) If you don’t want API security then you can select Disable option.
Note: you can get API sample code in developer section under API.