The step-by-step instructions for adding two numbers:

1. Write the two numbers one above the other, making sure that each place value lines up properly.
2. Start with the ones (units) column on the right and add the digits in that column together.
3. If the sum of the digits is less than 10, write the sum in the ones column of the answer.
4. If the sum of the digits is 10 or greater, write only the ones digit of the sum in the ones column of the answer, and carry the tens digit over to the next column.
5. Repeat steps 2-4 for each column, working from right to left.
6. If you carry a digit over from a column to the left, be sure to add it in to the sum of the digits in that column.