When you open the "Applications" menu on the left side of your screen, you will see the word "Withdraw" next to the position in question in the right corner.

If you no longer wish to participate in the selection process for a particular vacancy, just click on this term. You will then be directed to the reasons and feedback pop-up.

It is important that you inform the reason (such as low salary or too long process) that led you to quit and leave your feedback to help the company make the necessary adjustments for the next positions that will be opened.