The best resource for this stuff online and free is www.parktool.com/repair . Hover your mouse over the bike around the brakes and click. Follow the links to disc brakes.

Consider too that the kids Costco hires to assemble the bikes could very well have set up the brake caliper to the rotor with the front wheel not actually seated in the dropouts. So now you come along and put the wheel in correctly and now you're chasing your tail wondering why the brakes are not running smoothly. Bite the bullet and re-align the caliper.

The easiest way is to clamp the lever so it locks the caliper to the rotor. Now loosen the caliper bolts and give the caliper a bit of a wiggle so it finds it's "happy place" then lightly pinch down both bolts and then work back and forth tightening each a bit at a time so one bolt being tightened doesn't try to make the caliper walk. With that done you SHOULD have decent brakes.

Also note that since these will be mechanical disc brakes there is only one moving pad. The other pad is adjustable. To get the brakes to work their best that fixed pad has to be adjusted super close to the rotor. The slight waviness in the rotor will kiss the pad and sing it'll be so close. Some careful flexing to flatten the rotor can reduce or eliminate this brushing.