When adding numbers that have multiple digits, you first add the one's column followed by the tens, hundreds etc. For each column you put the result in the same column within the answer. Sometimes when adding two numbers together with multiple digits in either addend, you may find a situation where one of the columns adds up to an amount greater than 9.
Lets look at the example problem below:
46
+28
With this problem we start by adding 6 + 8 which results in 14. Since we can only put one digit in the ones column for the answer we must do something with the 1 digit of the 14. Since 14 can be broken up to being 10 + 4, 14 is in reality, 1 ten and 4 ones. Given this information we can take the 4 and place it in the ones column of the answer and since we have a ten left over we can carry that over to the 10's column.
1
46
+28
4
We can now add up the tens column 1 + 4 + 2 = 7. Since 7 is a single digit we can simply put the 7 in the tens place for the answer giving us an answer of 74.
1
46
+28
74