When adding integers with the same sign, add the values together and keep the same sign. For example, when adding two positive integers like 12 + 6, the values (12 and 6) are added together to get 18, and the sign (+) is kept the same. Similarly, when adding two negative integers like -5 + -8, the values (-5 and -8) are added together to get -13, and the sign (-) is kept the same.