Hi Ben,
I might be a little bit late with this, but here goes…
Follow the WSH path to the end. You will have to walk your bike down the stairs and bear left to take you under the WSH overpass. You'll be following Riverside Drive. Use caution crossing the onramp to the WSH.
Turn left (north) onto Staff Street. Follow it downhill (steep) to Dyckman Street.
Turn right (east) onto Dyckman Street. Follow it for 3 blocks to Seaman Avenue.
Turn left (north) onto Seaman Avenue. Follow Seaman for 4 blocks to 207th Street.
Turn right (east) onto 207th. Take it to Broadway/Rte. 9 and turn left (north). This will get you over the Harlem River. Be really careful around here: the road is beneath the train tracks and the steel columns that support them line both sides of the roadway. It is noisy and there are cars and pedestrians coming from every which direction. It is not a bike-friendly place to ride, and as of a couple of weeks ago when I last rode it, the top layer of the road had been peeled off for resurfacing. I'm guessing and hoping that by now that job has been completed.
When you have had enough of this, turn right (east) onto 233rd Street. This will take you over I-87 to a T-intersection with Bailey Avenue. Take a left (north) on Bailey. It will curve right and then left as it approaches Van Cortlandt Park South. Van Cortlandt Avenue West will approach from the right. Go straight across this intersection. You will soon see the offramp from the I-87 interchange on your left. Just past this, bear left onto the road which will take you under I-87. You will then be at the north end of the pond in Van Cortlandt Park. You will pick up the path on the west side of the pond. There will be an indistinct path through the grass where other cyclists and pedestrians have cut through from the road/parking lot to the path.
The first mile or so of the path is overgrown and rather rough. You might have to pull over to pass other cyclists and runners going the opposite direction.
I hope that this doesn't seem too confusing. You are basically making your way north and east, and avoiding some of the worst of the riding where possible (although the worst is the unavoidable section on Broadway/Rte. 9. You'll be fine as long as you are very careful.)
Greg