Answer:
The Incas structured their kingdom: There was a strong administrative structure in the Inca empire.
They controlled community welfare works. All regions used the official language: Runa Simi, later also called Quechua. They also use decimal system based census to verify their work and population. On the other side, if you mean how they expanded it: you should realize that there are several theories about the Tahuantinsuyo expansion phases.