Question

How would the location of the capital of the Empire help control it? (it's talking about Rome btw)

Answer 1

Rome was locatated in the center of the Empire, as a crossroads between the Western provinces like Hispania and Gaul, and the Eastern provinces like Egypt and Anatolia.

Rome also benefited from being located in the center of the wealthiest Roman Province: Italy.

We can see therefore, that Rome had one of the most benefitial geographical locations in the Empire.