I think what I'm looking for is Psalms 94-96 or 97... Maybe the whole twelfth Kathisma. I still don't know.
If anyone knows then please clue me in.
My understanding is essentially what ialmisry has said. The Lesser Entrance was quite literally the entrance of the clergy and people (and emperor, at Agia Sofia) into the church, and was the culmination of a grand procession during which psalms 91, 92, and 94 would be sung (although I have been taught that psalms 102 and 145, along with the Beatitudes, were a much later importation into the Liturgy from the Typika). What we have today is a situation in which the processional antiphons are still sung but the procession has been reduced to the servers and clergy, who by this point are already in the altar, processing out of the altar near the end of the processional antiphons, only to go back in again moments later to the singing of the Come, let us worship
, so the Entrance is not a true entrance at all. While the Lesser Entrance may no longer be functional, it is still in some ways the proper beginning of the Liturgy, and is rich in symbolism which is best seen at the hierarchical Liturgy, (which is the closest that we have today to the earlier form).