Once I georeference this map, how do I digitize it?
You will essentially be creating features of your desired type (points, polylines or polygons)
For PRO http://pro.arcgis.com/en/pro-app/help/editing/introduction-to-creating-2d-and-3d-features.htm
there is a similar page for ArcMap
That might be too busy of a map to do anything automated, but you may want to look at some suggested on youtube
How to convert scanned image to shapefile in Arcgis - YouTube or stackexchange. grass - Converting a .jpg map into a shapefile - Geographic Information Systems Stack Exchange Basically if you can somehow isolate the layers color you might be able to automate it.
Have you checked to see if the data layer you are looking for is available from the source of the map? Might be worth checking into before trying to recreate it.
Retrieving data ...