Assembly of New Bike
The details depend, but as a guide expect to install pedals and wheels and attach the handle bar to the stem (2 or 4 Hex bolts). Unless you are DIY challenged, the most time consuming part will be removing the packaging material from frame, handlebars, wheels. 

The disc brakes will (should) have packers that will needed removing. There might be plastic spacers in the forks and "plugs" to remove from the cranks where the pedals go in. 

Once assembled you need to tune the gears and check the brakes are working an aligned correctly. Check all the bolts and nuts are tight (use a torque wrench if you have one, else be careful - tight as in firm, not tight as in done up by a 600 pound gorilla holding a spanner)

If you have any doubts, your LBS will be able to assemble it for a about 1/2 hour labor charge.