You need to have a recent vesion of MATLAB, R2016 or later.
The Robotics Toolbox by Peter Corke has dependency on two other GitHub repositories: spatial-math and toolbox-common-matlab.
Install these libraries to the KUKA-SCARA-Simulation directory
git clone https://github.com/zlacey1234/robotics-toolbox-matlab.git --branch add_mdh_option_plot3d rtb
git clone https://github.com/petercorke/spatial-math.git smtb
git clone https://github.com/petercorke/toolbox-common-matlab.git common
To run the simulation, you run Simulation.m.