Check if the road is open on: https://www.doc.govt.nz/parks-and-recreation/places-to-go/marlborough/places/mount-richmond-forest-park/park-access/. I tkaes about an hour to drive to the top from staircase road turnoff and requires 4wd and all terrain tires recommended to reduce the risk of a flat tire. There is a marked path but this is nothing more than a couple of stakes in the side of the mountain. There is no well formed track. You will be climbing over rocks and walking over scree. It takes about 90min to walk the ~2km from the carpark to the summit. Don't underestimate how quickly the weather can change here.