[AngelicaDeAlquezar]

Using the personal pronoun or not depends on your intention: If you want to emphasize the person or to avoid a possible ambiguity in meaning, you use the personal pronoun. Otherwise, you don't.

Your sentence would most probably become "Sí puedo" (Yes, I can), to emphasize the fact that you actually can do something, in opposition to the idea that you may not be able to make it.