How to win points to enter more giveaways?

You don't win it. You have to wait, and you earn it when somebody makes a giveaway.

Read the FAQ for answers to common questions.

In this case, you wait, they build back up with time.

Points are generated automatically with time. Instead of trying to enter as many giveaways as you can,try to limit yourself to giveaway that are both for games you really want and that are have less entries(such as giveaways that only last one hour,or giveaways that are only available to group members) - this way you'll have a better chance of winning something and more points to spare.