Question

What methods did the Incas use to unify their large empire? PLEASE PLEASE ANSWER PLEASE I NEED HELP SO BAD

Answer 1

If you are talking about how the Incas organized their empire:  The Inca´s empire had a good administrative organization. The body of officials that, the, advised the Inca sovereign grouped and organized the population of the Empire. They regulated the works in communal welfare. All the regions used the official language: Runa Simi also later known as Quechua. They also verify their work and population using the census based on the decimal system.

On the other hand, if you mean who they expanded it: you should know there are several hypotheses on the phases of expansion of the Tahuantinsuyo. Some authors agree on the division of three phases. Each of the phases by different techniques according to the situation, organization and need at that time. The first expansion was the result of alliances that they used to expand their territories. The second and third was a result of conquers and internal  internal clashes.