How to implement the Skid Steering Drive plugin in Gazebo?

Hello, I'm new to Gazebo and ROS and wanted to implement the skid steering plugin from Gazebo for the a very basic 4 wheeled 'robot' , but I'm not sure what how the axis are supposed to be set and what some of the requiried variables truly mean e.g torque (not sure which number I should give as input) or broadcastTF (not sure why I should not want to broadcast) . At the moment I can drive backwards and forwards but it the robot does not turn. Here is the xacro that I'm using at the moment: and here the plugin:100.0/wheel_1_base_jointwheel_2_base_jointwheel_4_base_jointwheel_3_base_joint0.60.4base1cmd_vel0