How do you modify the velocity multiplexer for turtlebot?

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I have a Kobuki Turtlebot and would like to publish to the multiplexer on my own topic. The official documentation hasn't done me well explaining how to modify the parameters.

Where can I find the config and YAML files discussed in the documentation and how can I edit them? I am currently writing a rospy script for this, below is a simple implementation of what I'm trying to do.

#!/usr/bin/env python

import rospy
from geometry_msgs.msg import Twist

if __name__ == '__main__':
    rospy.init_node('CmdVelMux_test', anonymous=True);
    velPub = rospy.Publisher('/cmd_vel_mux/input/BSC', Twist, queue_size=10);
    Vx = Twist();
    Vx.linear.x = 0.1;
    while not rospy.is_shutdown():
        velPub.publish(Vx);
        rospy.spin;