Speak with your SharePoint administrator about your organization's SharePoint instance, and ask that person to consider adding a Power Pivot Gallery to the site. After you have access to a Power Pivot Gallery, you can upload your Power Pivot workbooks by following the same steps for publishing a standard workbook to SharePoint.
This figure illustrates a typical Power Pivot Gallery. Note that each workbook is shown as a thumbnail, providing users with a snapshot of each report. Clicking a thumbnail opens the report as a web page.
If you have an Office 365 SharePoint subscription, you have no option, unfortunately, for a Power Pivot Gallery, because Office 365 doesn't support it. This situation may change as Microsoft continues to add improvements to Office 365.