put the number that the decimal is over the place that it is in
example
.5
every space after the decimal is multiplied by 10
tenths place 0.1
hundreths 0.01
thousanths 0.001
etc
so .5 is in the tenths place so the fraction would be 5/10
the decimal is now converted into a fraction
another example
.07 is in the hundreths so it would be 7/100
final example
.25 is in the hundredths place since the last number lands on the hundreths column
it would be 25/100
if possible you can simplify if that is what is needed
