PowerPivot applications are created using Excel 2010 using PowerPivot add-in, You can read my post on configuring PowerPivot in SharePoint 2010 here. After creating a PowerPivot application then you need to upload it to SharePoint 2010 PowerPivot gallery so that it can share across organization. You should be able to preview the PowerPivot applications once you upload them to PowerPivot...