Hola Anupam

With the verb gustar you can never use the subject pronouns as a subject because with gustar in Spanish, the person who does the liking is not the subject of the sentence, so you'll always see:

me gusta, te gusta, le gusta, nos gusta, os gusta, les gusta

If you read the lesson again you will see that it is the "activity" that is the subject of the verb and the verb is agreeing with it.

Saludos

Inma