I just got my bike today and finished setting it up. As to be expected with every bike i've purchased, brakes always need tuning. Usually when you buy from a local bike shop, they take care of all that upon delivery so you never see these kinds of issues.
But this bike uses tektro Aries brakes, i simply looked the manual up online for setting up the brakes and it states that the pads should be 0.3mm on both sides of the rotor. I used my metric feeler gauges to set the tolerance. The right side uses an allen key to move the fixed pad into position, and i just used my feeler guage to move it between the piston and pad. I worked it in and back out until the feeler guage just passed through, albeit a little snug.
For the pad which moves when you pull the brake, that pad was pretty far from the rotor, at least 1mm out. So you have to loosen the cable with an allen key, swing the arm up and clamp down the cable again to move it closer. I did this a few times until i the feeler guage went through but just barely.
Once done, pick up the handlebars to left the wheel off the ground and spin. Should have no resistance or make noise.
PXpaul's method works assuming it was set to 0.6mm+rotor thickness gap between the pads from the factory. It's definitely the first thing to try. If it's not working, then you may want to do the proper adjustment.
If it's still a problem, then check your rotor bolts for tightness, and if that doesn't work, then your rotor is warped.