In this example, we have a list of people in Column A, and a list of hours in Column B:
To get all of Britney's hours, the formula is:
=SUMIF(A2:A7, "Britney", B2:B7)
The first part (A2:A7) indicates the data range to look for the value, the second part ("Britney") is the value to look for, and the third part (B2:B7) are the values to sum up.
This formula will show a result of 6, meaning Britney has 6 total hours in this dataset.