Hi Tim, welcome to TBN.
Are you thinking of making a full grapple...one that you remove the bucket and put on the grapple? Or are you talking about adding a bucket grapple to your bucket? Either way, you will need to add hydraulics to run it. You'll need either a diverter valve or a 3rd function solenoid valve. Some guys run the grapple off the rear remotes if you have those.
So let us know exactly what kind of grapple you're thinking of making first.