Without seeing it my guess would be
1) find out what type of quick connectors you have in back by checking the manual or with the dealer. Or maybe there's a part number exposed.
2) find out what type of connectors come with the grapple
3) determine the hose diameter you need, keeping in mind that you may want higher flow than a grapple up there at some point.
4) make or buy a bracket drilled for two bulkhead fittings (TBN search) that mounts on the crossbar connecting the loader arms. This is a mount for where the grapple hoses connect to your rear hoses. It will also give you a firm mount to push against if the connections are stubborn.
5) determine hose length by routing a garden hose between the front bracket and rear remote.
6) Take all that info to a hydraulic shop to make the hoses.
You may want to dig up your own bulkhead fittings to suit your bracket. I found them at Discount Hydraulics.
Search TBN. Tons of people have posted on their projects like this.