No one knows where the Inca originated from, however there are four myths at to how they came to be.
Tici Viracocha of Colina de las Ventas in Pacaritambo sent forth his for sons and daughters to establish a village. Along the way, Sinchi Roca was born to Manco and Ocllo, and Sinchi Roca was the person who finally led them to the valley of Cuzco where they founded their new village, therefore Manco became their leader and became known as Manco Pacac.
Another myth was that the sun god Inti ordered Manco Capac and Ocllo to emerge from the depths of Lake Titicaca and to built a city in Cuzco. By travelling by the means of underground caves until reaching Cuzco where they established Hurin Cuzco, or the first dynasty of the Cuzco Kingdom.
The third myth was that the Inca sun god told his wife that he was lonely so she proposed that he create a civilization to worship him and keep him company. Seeing this as a wise plan, he carried it out. The Inca were born from the Lake Cuzco and populated Andes as they worshiped the sun god.
In the last myth, Manco Capac was the son of the sun god and his sister Ocllo was the daughter of the moon. They were sent by the sun to look for a place to build an empire. Along their journey they had a special rod entrusted that it be with them at all times for it will sink into the ground once they are at the right place. In short, the rod told them here they were to create a new city and it sank into the ground in Cuzco.