Looks like you need an owner's manual.
http://www.samarins.com/maintenance/manual.html is a good source for an owner's manual. A salvage yard and E-Bay are also sources.
If I remember correctly, you have to pull out the radio buttons that don't correspond to #1 through 6. Hold it out for a while and it will begin to change the hour or the minute.
This depends on the condition of the car, miles, numbers matching, had it been tampered with, interrior condition. Over all if your looking at a 85 Lesabre just to drive around as an every day car...
Turn on the power knob for the radio/clock. Wait until the clock display shows up. Press "set", and use the "scan" and "seek" buttons to set the time. Hope this helps!