We use capital letters at the beginning of sentences, for names of people and places, and for days, months, and festivals. The document provides examples of when to use capital letters and practice questions for students to rewrite sentences with proper capitalization or fill in names, days, months, and festivals. It teaches that we capitalize the first letter of sentences, the pronoun 'I', names of people, places, schools, cities, and countries, and days of the week, months, and festivals.