Joining QGIS Property Parcel Mapping shapefile to an Excel file and displaying symbol in Parcel Mapping Shapefile

I am assuming that you could either set a label or a custom symbol in the center of the polygon. For the label simply use the field that you have joined. If you want a custom symbol you can do it in 2 ways, either export the centroid of your current layer using the tool in the processing toolbox (this will also export the joined excel table to the new file). Another way is to go in the symbology, use categorized geometry, for the symbol use the geometry generator to get the centroid (see image) and don't forget to lock your base style to prevent it from changing.

Though if you are using the geometry generator your symbology will be altered in the legend, if you have a legend.

Is this what you wanted?

Ken, first ensure your join has been correctly set up. Right click on your layer then in Properties / Joins you should see a listing of the join(s) existing on your layer.

If the join is correctly set you can then open your attribute table you should be able to see the additionnal attributes coming from your joined layer (your xls file).

You then decide what you do with these extra data ! A common choice is to setup a categorized symbology (properties/symbology/categorized) based on the attributes you joined (choose the right column for that).

Care about the relation existing beetwen your 'properties' and your excel file (1-1 relation or 1-n relation) ... if it's a 1-n relation you'll certainly have to aggregate your data (by "properties") to help qgis understand what you want to map ...