This comprehensive page on transport to and among the islands is part of the Visitor's Bureau website.
Once you're in Friday Harbor:
Getting off the ferry, you'll be directed to Friday Harbor's main street, Spring Street. Take it up the hill -- about a mile.
At the yellow coffee drive-through, turn left on Mullis street, and take it out of town (South). In about a mile it becomes Cattle Point Road.
About four miles down, turn left on Jensen Bay Road.
One mile down, turn left again on Halsey Road.
We're second driveway on the left, 259 Halsey Road. The post says "Chadwick" and has two reflectors on it like eyes.