I see that you already have a MATLAB license and want to install the Signal Processing Toolbox.
You can refer to the following MATLAB Answers post to help you with the installation of the Signal Processing Toolbox: https://www.mathworks.com/matlabcentral/answers/458125-where-is-signal-processing-toolbox
More details about the Signal Processing Toolbox can be found here: https://www.mathworks.com/products/signal.html
I hope this answer will help resolve your issue.
