Locate the Xara Picture Editor folder in your Program Files. More info.
You will find a 'PSplug-ins' folder inside this.
Copy the Photoshop compatible plug-ins (make sure you include all the files) into the folder called PSplug-ins. We recommend that you create sub-folders inside for each plug-ins, so the full path will be like this:
Xara Picture Editor\ PSplug-ins\ plug-in name 1 plug-in name 2 plug-in number 3