819 ÷ 4 = 204 R3
We're going to perform division on 819 with 4 as the divisor.

Step 1:
4 goes into 8 2 times with a remainder of 0.
Write down 2 as next digit of of the result. 
Result so far: 2
Subtract 8 from 8 to get 0.
Bring next digit (1) of the dividend behind the 0 and repeat the process: 1 / 4

Step 2:
4 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 20
Subtract 0 from 1 to get 1.
Bring next digit (9) of the dividend behind the 1 and repeat the process: 19 / 4

Step 3:
4 goes into 19 4 times with a remainder of 3.
Write down 4 as next digit of of the result. 
Result so far: 204
Subtract 16 from 19 to get 3.

The final result is 204 with a remainder of 3.