Excel Power View reports encourage you to drag the elements you need for your chart onto the report surface in the way of a table first, then you can convert that table to a number of different chart visualisations in a second step.
Having trouble converting to a chart ? First you need to have something worth aggregating in your table otherwise you won’t get an option to convert to a chart. Secondly, make sure you click on any cell within the table, then a Design tab will appear in the ribbon somewhere between the Power View and PowerPivot tabs.
Click on the Design tab, then on the left choose from a number of different visualisations under the “Switch Visualization” section of the ribbon. Note as you select each of the different charts, you may get a slightly different menu of Power View fields on the bottom right hand of the screen in which to configure and drive the chart.
For Pie charts remember they are bad (http://www.stevefenton.co.uk/Content/Pie-Charts-Are-Bad/) but if you still want to be bad, they can be found under “Other Charts”. Remember however that Power View Pie Charts currently don’t support Data Labels (http://office.microsoft.com/en-au/excel-help/pie-charts-in-power-view-HA103230547.aspx) so if this all sounds a bit shady, try a column chart.
Go forth and Visualise !