1. Open Microsoft Excel, and click on the 'Office' button.
2. Click on 'Excel Options' located at the bottom right corner of the Office menu window.
3. Select 'Add-Ins' from the vertical navigation bar on the left of the 'Excel Options' window.
4. Check the boxes next to the add-in programs you would like to download, and then click 'OK.'
5. Follow the installation prompts to install the add-ins, and then click on 'Add-Ins' located in the toolbar at the top of the Office Excel page to load and use your add-in programs; you can also access them through the data, formula and add-in tabs.