Draw the old fluid out of the master cylinder reservoir and fill with new DOT3 or DOT4 brake fluid. I like ATE (blue one time, amber the next) or Valvoline.
http://www.fcpgroton.com/volvo240brake.htm#fluid
Bleed the brakes in this order until new, clean fluid appears...RR, LR, rear proportioning valve, RF, LF. Don't let the reservoir go empty and suck air into the system. Test the brakes, If the pedal is spongy, bleed again to remove any air bubbles you missed.
Ken