Well, you can use a calculator...
But if you mean how to divide w/out a calculator, then
divide in the same way as a regular number; just put the decimal point in the correct place.
For example,
0.246/2
would be
0/2 =0
*decimal point*
2/2 =1
4/2 =2
6/2 =3
So it would be 0.123