The Yorkshire Arboretum is part of the Castle Howard estate, and the entrance to the Arboretum is opposite the entrance gates to Castle Howard.
A website describes the Arboretum, and there is a comprehensive map to help you plan a visit.
All walking is on easy, level paths.
There are plenty of rest benches.
There is also a visitor centre with a cafe / restaurant, shop, and toilets. Outdoor seating is available.