1023 ÷ 4 = 255 R3
We're going to perform division on 1023 with 4 as the divisor.

Step 1:
4 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 1 to get 1.
Bring next digit (0) of the dividend behind the 1 and repeat the process: 10 / 4

Step 2:
4 goes into 10 2 times with a remainder of 2.
Write down 2 as next digit of of the result. 
Result so far: 2
Subtract 8 from 10 to get 2.
Bring next digit (2) of the dividend behind the 2 and repeat the process: 22 / 4

Step 3:
4 goes into 22 5 times with a remainder of 2.
Write down 5 as next digit of of the result. 
Result so far: 25
Subtract 20 from 22 to get 2.
Bring next digit (3) of the dividend behind the 2 and repeat the process: 23 / 4

Step 4:
4 goes into 23 5 times with a remainder of 3.
Write down 5 as next digit of of the result. 
Result so far: 255
Subtract 20 from 23 to get 3.

The final result is 255 with a remainder of 3.