It is important to understand the vitality of correct punctuation and use of capitalization when it is necessary. Capitalization allows you to properly write the personal names of things and people and gives them the correct importance within a sentence. Also, punctuation is vital. An idea within a sentence can change entirely when you use the wrong punctuation and can alter your meaning, even causing trouble for the writer and misunderstandings.
The correct writing of this paragraph then, would be thus:
When you visit Yosemite National Park, be sure to identify the peak of Mount Whitney in the distance. It´s the highest peak in the continental United States. The park rangers (who work for the NPS) are helpful. Ranger T.J Smith says: "We are here to help!".