If you are adding like fractions than you just add the numerator. If you are adding related fractions then you change the denominators so they match. When you change them you have to divide or multiply the numerator by the same number that you divided or multiplied the denominator by.

I think we learned about equivalent fractions. We also learned about putting fractions in order and learned tricks to help us like changing the denominator or the numerator and we learned about making a model or circle to help us understand the size of the fraction.