Option 1: Modify your C++ code so that it writes the data to a comma delimited file, where the first column is the simulation time and the remaining columns are the output values for each time step. Then, use one of the options discussed here to bring the data into Simulink. https://www.mathworks.com/help/simulink/import-data_import-data.html
Option 2: Create a new Simulink S-Function block that will run our code and has output signals for each of the variables your C++ code computes. This is more of an advanced maneuver. https://www.mathworks.com/help/simulink/slref/c-object-methods-as-legacy-functions.html
