Vedic rituals were not the pujas which you associate with hinduism to day. They were fire rituals on a small a or on a massive scale. altars, fire would be lit offerings would be given to vedic deities. Priests of different categories would chant mantras embodied in vetas. The idea would be to get certain benefits - worldly or other worldly.
Swami Sarvapriyananda teaches the Katha Upanishad, which is one of the most popular Upanishads. The scripture concerns the story of a young man who goes to the house of death to find out what happens after death. The reply describes the nature of reality and the meaning of life.