Note:

•   Don't leave blank rows or columns when entering your data.
•   A pie chart is a percentage chart, so only one series of data will be used in the chart. If there is more than one column of data, try to list the data to be used in the chart next to the column containing the list of names in order to simplify creating the chart. 

Step 1: First create excel sheet with some dummy data as below 

Step 2: Now select data which you want to display into graph. Here I have selected rage of data from B6:C11. Now select pie chart option from “Insert” tab as below image

Step 3: After selecting pie chart option, chart will be display as below

Step 4: If you change style of pie chart then select pie chart (which you created in step 2) and chose formatting tab according your choice.