A downhole tubing string and an umbilical harness are combined in a wellbore. The umbilical harness, which is formed remote from the wellbore, includes an umbilical, and umbilical connectors connected to lines in the umbilical. Connectors attach to well components and make up part of the downhole tubing string. The well components include valves, sensors, and actuators. The umbilical connectors attach to the umbilical at strategic locations so the umbilical connectors can reach and be mated to corresponding component connectors when the umbilical harness and downhole string are combined. Electricity, communication signals, or both, are transmitted along the lines in the umbilical, which are selectively conveyed to each component via the mated connectors. As the umbilical connectors are installed on the umbilical prior to wellsite delivery, the umbilical harness and downhole string are combined by engaging plugs on respective ends of umbilical connectors and corresponding ends of component connectors.