The number on the left is the one we're dividing by, the one "inside" is the one we're dividing.
The answer goes at the top.

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2|1

How many times does 2 go into 1?
0
So we write (don't forget the decimal point!)

  0.
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2|1.0

Now we have added a 0 on, because there were no digits left.
So how many times does 2 go into 10?
5
So we have

  0.5
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2|1.0