When doing long multiplication, allot take is patience for each number. Let's take for example the following:
123456
x 4
_____
We do 4x6.
The carry any numbers.
Then 5x4.
Carry any numbers.
4x4.
Carry any numbers.
4x2.
Carry any numbers.
4x1 is 4 obviously.
When carrying numbers, we would have to remember to add the numbers that were to be carried. And therefore, this would be an example on how to do long multiplication.