Warning: Cannot modify header information - headers already sent by

[q2amarket]

I am using this library with WordPress theme. When I try to render form it is giving me following error.

Warning: Cannot modify header information - headers already sent by (output started at path\to\wp-includes\formatting.php:4971) in path\to\Zebra_Form\Zebra_Form.php on line 4175

Fatal error: The library tried to store the CSRF token in a cookie but was unable to do so because there was output already sent to the browser. You should either start a session prior to instantiating the library (recommended), have no output (including and tags, as well as any whitespace) sent to the browser prior to instantiating the library, or turn output buffering on in php.ini. in path\to\Zebra_Form\Zebra_Form.php on line 4176

Any solution?