I'd use a Snap Pour Point (see link below) with the "pour point" point feature class for the best results. If I remember correctly, one can do a Watershed without using Snap Pour Point in locating the points, but in the past I got weird results sometimes, whereas with Snap Pour Point it was good.
Better results will be obtained if the Snap Pour Point tool is used beforehand to help locate the pour points to cells of high accumulated flow.
ArcGIS Help (10.2, 10.2.1, and 10.2.2)
In this case Flow Length is not needed for Watershed, so you can skip that one.
As for the Flow Accumulation, the diagram shows it connecting back to Watershed through Stream Link, but I am not recalling how that fits back into Watershed and not seeing it as an input. It's been a couple of years since I ran this, so will have to scratch my head and try to remember what the connection is. Maybe someone who has worked with this more recently can comment on the Flow Accumulation - Stream Link connection to Watershed?
EDIT - Figured out part of it. The Snap Pour Point (Spatial Analysis) process needs Flow Accumulation as an input. Still not sure about the Stream Link connection, though.....
ArcGIS Help (10.2, 10.2.1, and 10.2.2) - Snap Pour Point (Spatial Analysis)
Chris Donohue, GISP