We know about the Wari and Tiwanaku state because they left behind cities and monuments, temples and burials, arts and crafts, fields and quarries, and all the other material remains that any civilization does.

I've talked before about what material remains can tell us about ethinicity and religion at Tiwanaku. This answer gives a general overview of the Tiwanaku capital city.

Is there anything more specific about these cultures that you are interested in?