Go to the Simulations Tab and navigate to the TB2 simulation and start it.
roslaunch tb_wall_avoider start_training_wall.launch
And you will see the robot start learning using Qlearning(RL).
cd ~/catkin_ws/src
git clone https://github.com/shivangg/tb2_avoid_wall.git # to clone this repo
cd ~/catkin_ws # catkin_make always run from this location
catkin_make #to compile the package
source devel/setup.bash
roslaunch tb_wall_avoider start_training_wall.launch