The New Frontier Brand of muzzleloader is the same models as CVA. The Wind River is a CVA BuckHorn with a new name basically. Go the CVA website and download the manual for the Buckhorn Rifle. That will tell you how to disassemble it.

Basically the back lock nut screws off. Be careful, there is a spring under that. After you remove that, pull back on the bolt and then depress the trigger and push the bolt and spring out of the rifle. You can now push a long screw driver or the correct breech tool in there and turn the breech plug out. Depending on what breech plug you have, some were slotted so a screw driver could remove them. Others had a hex head so thick walled deep socket could be pushed past the trigger (again, depress the trigger, very important) and then with the socket and ratchet.. bring the breech plug out.

The problem you might be facing is.. the breech plug may be stuck if the rifle was never cleaned. So you can take the barrel out of the stock by removing the locking lug bolts on the bottom. Take the trigger assembly off the bottom of the barrel. and then put the barrel lug portion in a vice.

Sometimes you can pour boiling water down the barrel to help free the breech plug. Others put things like WD 40, Kroll Oil, Liquid Wrench, even strong cleaner. You're trying to break the soot deposit from the prior shooting free.

If all else fails, mail the barrel back to CVA and let them remove the breech plug for you.