If the company you applied to has enabled candidates to withdraw their applications, and if the application deadline has not passed yet, you can log into your Grade Varbi account (https://profile.varbi.com/) and update your application under 'My Applications'. If that option is not available, you will need to contact the employer.
Employers are data controllers, and therefore they must receive your request for deletion. Contact information for the employer is usually available in the job advertisement, or if you are logged into your Grade Varbi account, you can respond to the latest message you have received from the employer.