The PCT wanders in and out of the NP along this common part of the trail and is administered by the USFS for its length with the NP which means the USFS rules on the trail and USFS camping rules on USFS land, but no camping on NP lands.
The trail crosses highway 410 at Chinook Pass, with the trail over the new walkway bridge over the highway where there is a trailhead on the USFS side of the boundary and the Tipsoo Lake picnic area on the NP side a short distance west of the bridge.
For hikers there are several options to accessing the PCT which you can find information on the description and map of the PCT along the boundary with the adjacent wilderness area. There are several good dayhikes as well as overnight to longer backcountry hikes, one being the loop of the PCT and eastside trail along highway 123.
Anyway, the stuff is there. Let me know if you find problems, have questions or suggestions with the Web pages.