2014 Diamondback Jr. Viper Brake Problem
This bike looks to have a vee brake seen on (now old school) mountain bikes.

The popping noise you notice could be the cable housing not sitting in one of its barrels. And, pulling the lever that could cause it to move suddenly in/out of place. It  could also explain why the wheel isn't turning well: the housing could pull on the cable, and hence the brake. Check the housing, if it keeps falling out of the those little barrels, it may be because the housing is excessively long. Have REI shorten it for you -- you can do it yourself, but you'll need something more than those needle noise pliers. ;)

If that's not it, check the wheel. Ensure it's sitting center in the frame. Lift the bike and turn the rear wheel, if the brake pads are really close to the rim, then you will want to give out a little slack to brake cable. If one pad rubs, adjust the amount each brake arm's spring pulls outward. (There should be a small screw on the side of each brake arm.) I like to balance the spring tension, so if you tighten one arm, loosen the opposing arm.

Hope that helps.