Find all the information you need here:
Be sure to also download and read the FAQ PDF found on that page.
Follow the training offered by Qlik and get a few weeks of hands-on experience with the product. In case of the Administrator exam, some general experience with servers will help you.
If you know what you are talking about when it comes to Qlik Sense, you should be able to successfully make the exams easily. If you have no clue or the habit to keep using the names and methods of other tools, you will fail.
Note that sharing the exam questions is illegal (which people have signed for not to do before doing the exam).