This is done in the program Logism.

Create a logic gate with inputs for 2 bits, and a carry in, then outputs the sum of those 2 bits, as well as giving us a carry-out.

1. Create two inputs and label them A, and B

2. Create an output called Sum

3. Create an extra input called carry in, and an extra output called carry out

4. If and only if A is 1 or B is 1 or carryIn is 1, set sum to 1

5. If A and B are 1, set sum to 0 and carryOut to 1

4. When the result of your addition overflows, put that overflow into your carry out