in principle you point the xara program to the folder the plugins are installed in:

in xdp that is menu utilities/options effects and plugins tab - click on setup, click on add folder and navigate to the folder you want to add [the folder, not inside it], click ok, make sure enable host specific plugins is ticked, and click ok

you can set the effects options if you wish, click apply and ok

you may need to restart the program - you can add more than one folder