No special access issues
There can be grasing sheep or reindear in the area. Make sure to leave them undesturbed and remember to close the gate when you enter the area from the parking.
Mjelle is a popular place for family outings especially on weekends on good weather days as it is very child friendly, so make sure to keep your noice level down and behave politely. And as always don't litter.
Park at the designated official parking and walk in from there on the clear path. You can see all the boulders from this path along the way in.