Put In below the home of Brown
"Put in" as a nautical term refers (in this instance) to docking a boat. The next place along the Green River is Colorado and shortly after entering Colorado there is a boat ramp. The boat ramp is in the Brown's Park National Wildlife National Wildlife Refuge. The "ramp" is simply a road that is cleared into the river.
Put In - boat ramp on north side of Green River, South of Brown's Park NWR.
Could it actually be this simple?