Depends on the temperature it's been conditioning.
I'd hook it up to serving pressure and draw a glass. If it's perfect (I think it's too early), then leave it alone to chill.
More than likely, it won't be quite ready.
I'd go ahead and hook it to gas in your chiller. Set the PSI to about 15 and then test it every 12 hours.
You are probably about 50-60% of the way to being carbonated.
If by Friday it's still not carb'd enough...crank the gas to 25 and check it every 2-3 hours. Once you can pull a decent glass (good head, effervescing bubbles, lacing on the glass), set the pressure back to serving and release the excess pressure in the keg.
IMPORTANT NOTE: Before these taste tests, shutt off the gas (or manifold valve), bleed the excess pressure from the keg...set PSI to serving and then draw a sample.
Too high a pressure and you'll get foam and may be led to beleive that foam = carbonation.