No special access issues
There is a road fee of 25,- NOK. When driving into the forest, you'll see a road barrier (red and white arm to close the road, ish located here https://maps.app.goo.gl/rnjPGBWXCJG1tHGt6). Here you'll find information on how to pay. Make sure to do this so you dont get a fine. Drive until the road ends. The trail to walk is straight ahead when you drive in. The sign says "Mørkholtet". After around 9-10 minutes of walking, it will come a sign, where you take left towards " Røsåsen Kongsgården". After taking left, it's around 1 minute of walking to Kongsgården. The sign is small, so make sure to look for the sign. Under photo's there is a picture of this sign.
Parking location: https://maps.app.goo.gl/rnjPGBWXCJG1tHGt6