Write down the fraction you wish to put in radical form.
Simplify the fraction down as low as you can, this may end up yielding a whole number. You can simplify a fraction by finding the highest common denominator, or the highest number that both the top and bottom number of the fraction can be divided by. Once you find that number and divide both numbers you will have your fraction in simplest form.
Write down your simplified fraction or the whole number that was derived from the original fraction and put it under the square root symbol. This is your fraction in simplest radical form.