1 - Find Electrical Parts for Carlos's Invention.
Carlos can be found at the Bazaar, Trinity Territory.
For his invention to work, he needs 1x Electric Parts. It can be found either at the Hardware Store at night or at the Military Patrol.
Both are nearby and can be spottet by binoculars.
I was lucky to have already some in my inventory from the previous Main Quests.
2 - Turn on Carlos's Invention.
The switch for the invention is in the outside area of the Basaar near the main gate at the west.
3 - Watch the electric fence demonstration.
Carlos is also in the safe outside area of the Bazaar. He and the goat are near the north eastern side exit.