In order to turn a fraction into a decimal, you simply have to complete the fraction by dividing the numerator (the number on top of the fraction) by the denominator (the number on the bottom of the fraction).
For example, say we have the fraction

. All we have to do to convert it into a decimal is divide 1 by 5.
1 / 5 = 0.2
So, the fraction

written as a decimal would be 0.2.
Hope that helped! =)