There are two ways to use them. First print out the sheet onto some white card and cut out your chosen petal shape. If you want to use the template to cut against the crease as in the No Tools Flower tutorial, then carefully cut exactly down the middle lengthwise to give a half shape. Now use it as per the tutorial.
If you want to cut them out more quickly, and without a crease down the centre, then use this method:
Take a strip of paper, a little wider than the length of the petal and draw round the whole petal shape at one end of the paper.
Fold the paper, concertina style, until you have four layers including the one with the petal drawn on it.
Hold all the layers together firmly, whilst you cut around the lines of the drawn shape. Cut just a fraction inside the line, so that there will not be a mark around the edge of the top petal.
Using this method, you will only have to draw and cut three times to get twelve petals. Fairly quick, and quicker than the crease method.