You may have noticed from the first dialogue that there is no need to use the subject pronoun (e.g. I, you, etc.) in Spanish. The ending of the verb tells the listener who you are referring to.
Soy Laura I am Laura ¿Eres Carmen? Are you Carmen? Es Juan He is John
However, if you want to emphasize whom you are talking about, or
talking to, you should use the full form. That is, use the subject pronoun (i.e. yo, tú, él, etc.).