How do the inca first react to the arrival of the Spanish

The Inca had a large population and were themselves expansionist, and were in the process of conquering and integrating much of the rest of Central America when the Spanish arrived. They made some effort to be civilized, and would try to negotiate peace rather than engaging in total war---but still, they were imperialists.

The Inca were initially relatively welcoming to the Spanish explorers, trying to open diplomatic relations with them. They didn't realize that their recent plagues were due to new diseases from Europe, nor that the Spanish had no particular desire for diplomacy or compromise.

But the plague (most likely smallpox) threw the Inca into disarray, and exploiting this advantage along with their technological superiority the Spanish swiftly conquered the Incan capital Cusco. The fact that so few were able to so decisively conquer so many is still a little baffling to historians.

There were subsequent revolts against the Spanish and a series of civil wars; but the Spanish ultimately prevailed. Eventually the Spanish-controlled governments in the region became independent states such as Chile and Argentina.