To install branch circuit wires, use a fish tape to pull in the wires. If you are installing NM wiring, install NM connectors to the electrical panel and secure the wires with the two screws on the straps. Strip the outer sheathing to expose the conductors.
Connect all of the green and bare copper wires to the ground buss bar. Connect the white neutral wires to the neutral buss. If you bend the wires ahead of time, you'll have a nice, neat wire installation that looks uniform.
Next, install the circuit feeds to the branch circuit breakers. The black and red wires are the feeder wires in this photo with the black wires being one of the hot feeds and the red wires being the other. Connect the appropriate sized wire to the correctly rated breaker. Bend the wires so that they keep a neat appearance when the installation is complete.