first of all in the Power Point when u want to make a chart :
Go to that slide and the click the chart button from the tools up like this >>>
then you will get a Bar chart and a data filling space, right click on the Chart and then choose chart type . Choose Pie chart and click ok . Now in the space where u will put your data information for the pie ,, remove everything thats there 'cause for pie u only need the first 2 rows. ( the first for the names the second for the numbers.) like this >>>
when u do that u will get your chart, ofcourse u will have to modify it i mean make it bigger so it fills the whole white area and like that and make the text clearly visible and so on.
if you didnt follow any step your welcomed to ask =]