Students are often confused by the difference between 'false' and 'not given'.
You should choose false if the information in the passage directly contradicts the question statement; in other words, you need to be able to show that a different answer would be true. Choose not given only when there is no information, or not enough information.
Click here to see two example questions. The answer to the first one is 'false', and the answer to the second is 'not given'. Hopefully my explanations will help you to see the difference.