Once Shapefile is uploaded, How to use longitude and latitude data

I created a shapefie from a portal item in Arc GIS. So, on Matlab, I have this map:

The shapefile I have is called "Sewershed.shp".

I type in:

shaperead('Sewershed');

Then, I get a 17x1 structure

So, the heading, "Bounding Box" are the longitude and latitude boundaries that defined the Sewershed (under heading "SewerShed")

The polygons in the map I showed above are the outlines of the sewer shed.

Now, I have an Excel spreadsheet that lists items as defined by longitude latitudes. I need to identify which Sewer Shed each item belongs to.

I appreciate any help! Thanks.