Set them aside and spread them out someplace dry and they will ripe. I have tons of black walnut trees on the property and we get a bumper crop every year, along with paw-paws, buckeyes and a few others. Working on acorns, which no one in the valley that I know of are successful getting one to grow to its maturity. I'm a little hard-headed because I'm giving them another go in the front yard. So far so good. Plan on planting more. I have one in the woods at one of my hunting locations that should be ready to produce any year now. Haven't been over there since winter time so, I hope to see acorns over there when I make my way there this year.