There are a number of reasons you may want to withdraw your application from consideration.
To do so, navigate to the application tab and locate the application which you would like to withdraw.
Once you have located the vacancy, clicking on it will show the information for this role. In the top right in red you will see an option to 'withdraw application'. Clicking on this you will be prompted to select your reasoning for withdrawing. Choose this and clicking the withdraw application button will now completely withdraw your application from this vacancy.