A lot of Excel procedures are packaged in Add-Ins. An Add-In is basically a workbook containing some code, that has some other unique properties. The workbook is invisible. The workbook can be installed, which means it opens when Excel opens, so that its functionality is always available.
Installing an Add-In is really not complicated. If it came in a zip file, unzip it into an appropriate directory. You can use any directory you want. Excel has one or more default add-ins directories, depending on version:
C:\Program Files\Microsoft Office\OfficeXX\Library
where XX is 12 for Office 2007, 11 for 2003, and so forth, and
C:\Documents and Settings\UserName\Application Data\Microsoft\AddIns
where UserName is the user’s Windows account name.
With Excel running and any workbook open, go to Tools menu and choose Add-Ins. You will see the following dialog, which lists the add-ins Excel thinks are available. Any installed add-ins are checked.
If the add-in is saved in one of the default add-ins directories cited above, the add-in will be listed in the dialog, and you can check it to install it. If it isn’t listed, simply browse to select the add-in, and it will be added to the list and checked.
Below the list of add-ins, you will see the name and description of the selected add-in. Click the Okay button, and the add-in is installed and ready to go.
To uninstall an add-in, simply open the Add-Ins dialog and uncheck the add-in.