These used a separate valve in series with the main control valve. The main valve would have to have a power beyond sleeve added if it is not already fitted with one then the second aux valve could be plumbed in the the power beyond flow from the main control valve, then the out flow connected to the return port on the tank. Case has plumbing schematics online in there parts cat, go to www.casece.com and look up your model. That said it would be much easier to buy a machine with aux already.If the spool is in place, you may only need hydraulic lines and a linkage. If the spool isn't there, you are up for a fair amount of money and trouble working out how to hook something up. If possible, get a machine with it already installed.