Are you looking to get the sum of a field in your point feature class into your polygon feature class? For example, if you have a Cities feature class with the field Population, and a States feature class. You want each state to have a field that represents the sum population of all cities that are within that state?
Take a look at the Tabulate Intersection tool. This will create an output table that you can join back to your polygon feature class, and then calculate over the summed values.