Question

How do you add two different signed integers

Answer 1

You don't have to add you need to subtracts them cause they are different singed integers and then you add

Answer 2

Here’s an example from what I am understanding from your question.
I use a number line to help me. If you were adding 5 to -4, you would go down with the negatives to 0 and then add the remaining positive numbers you have. Get what I mean???