You discovered someone and want to tell them "I like you"? Then swipe right and give a like.
If you want to see who likes you, then you can easily take a look. Go to "News" in the app or on the website (bell symbol in the right corner).
Likes are blurred? You can unlock these with credits. Premium allows you to discover them straight away.
If you use Premium, you can find an overview of the likes you've given in the profile view.