To withdraw your application you will need to do the following:
In your jobseeker account, click on "Sent applications" in the menu to the left. From there you can find a button to withdraw you application.
If the deadline for the vacancy has not passed your application will be withdrawn automatically when you do this. You will also receive a confirmation in your mailbox.
If the deadline has passed, the employer will have manually handle your request to withdraw the application. You will receive a confirmation in your mailbox ff the request is granted.