To convert decimals to fractions, simply turn the decimal into a fraction by putting it over one, multiply it by 1 (in the form of tenths, hundredths, thousandths, depending on how many decimal places), and simplify the resulting fraction if possible, or necessary.
Since 0.25 is the same as 25/100, find the GCF, which is 25 and divide it on the top and the bottom. 25 divided by 25 is 1, and 100 divided by 25 is 4. So in simplest form, your answer is 1/4