Split the sheathing on the cable leaving about 1/4in still covering the wires. Cut the sheathing to remove it and strip off about 3/4 inch of the plastic insulation from the end of each wire. Avoid nicking or scratching the copper wire while removing the insulation.
This page offers some options for locating an electrical source for a new wall receptacle or a light fixture, and running the new cable required. To make this job easier, it’s best to have a second person at one end or the other of a new run, to sight the end of the fish tape and help guide cable. Also be sure to always turn off the affected circuits before working on household electricity.
Hold the outlet box against the ceiling about midway between the joists and trace the outline with a pencil. Cut a channel from one joist to the other, the same width as the outlet box. Use a drywall saw to cut gypsum board and a reciprocating saw to cut wood lath plaster.
Try to remove the wallboard cleanly so it can be reattached when you’re done. The baseboard can be reinstalled without replacing the wallboard, but this will create easy access for pest such as rodents, as well as drafts from cold air during the winter.