After the parades were done, the natives were baptized in view of the Monarchy. After that, people generally stop talking about them and they were most likely given as slaves, like the rest of the shipments to Spain.

For early sources, we have two 'reliable' and generally primary sources: The True History of the Conquest of New Spain and The Florentine Codex. There's also the account by Gomara and the letters from Cortes to Spain, both of which are rather more biased. Letters with a really long title, '24, Unnamed letter, '22, and Gomara's works

Where can I find original sources, hopefully on the Internet?

Unfortunately, I can't help you with your main question, but I can offer some suggested reading for you.

The Four Voyages of Christopher Columbus. There are also older editions that you can read online, in part if not in whole. You can also find the letter Columbus wrote to the King and Queen of Spain upon his return to Europe here.

Some additional books you may find interesting. I tried to pick editions that you could read in full (though one requires a university log-in or equivalent), or at least get a substantial preview of. Here they are in no particular order:

• Jacques Cartier: His Life and Voyages
• Verrazano's Voyage Along the Atlantic Coast of North America, 1524
• The Journey of Alvar Nuñez Cabeza de Vaca
• Narratives of the Career of Hernando de Soto
• The Coronado Expedition
• A Description of New Netherlands
• The Jesuit Relations
• History of a Voyage to the Land of Brazil
• André Thevet's North America: A Sixteenth-Century View.