Installing V4 Add-Ins
Installing and managing the add-ins is very easy, via the "Tools -
Add-Ins" menu.

The next dialog lets you Insert, Remove or disable add-ins

To install an add-in, you hit "Install", browse to the folder where you've
downloaded the add-in, select the .xadd file and click OK. You then get a
dialog asking whether you wish to enable it. Installation complete!