I came across an article which mentioned that various blockchain services and cryptocurrency exchanges reward new users who register through certain referral links. Now I want to claim these bonuses. Where can I find these referral links?

Referral links usually benefit the people who share them much more than those who sign up through them. The new users get only a small bonus. Of course, it also depends on where you register. You can explore different crypto referral codes here: https://icoda.io/referral-codes/ . Check the bonus terms and decide for yourself which platforms are worth signing up for.