North Lagoon Drive runs along the north side of Lost Lagoon. Since Stanley Park Drive is mainly one-way, this section of road is used to connect Stanley Park Drive at Second Beach to Georgia Street thereby exiting Stanley Park. It is a beautiful forest-lined road with a bunch of parking spots along the way.
To get onto North Lagoon Drive turn left or right (because Stanley Park Drive is one-way both directions at this intersection) from Stanley Park Drive at Ceperley Meadow.
There is street parking along most of North Lagoon Drive. Here is more information about parking: Parking in Stanley Park