Clark,
You can zoom/center a map in a Web AppBuilder application using x,y coordinates.. Just add ¢er=x,y to the end of the URL for the application.
Use URL parameters—Web AppBuilder for ArcGIS | ArcGIS
You can also enter an X,Y coordinate pair into the Find address or place search box to do the same as above.
And another option, use the GeoLookup widget (currently in Beta) to drag a CSV containing the lat/long onto the application and plot the points.
GeoLookup widget—Web AppBuilder for ArcGIS | ArcGIS
Kyle