The 'addpath' is not a common tool - at least I think so, because it's not part of any Linux system that I used so far (it's also not on my current Fedora). Generally
is the method to add a new entry to your $PATH variable, where each path segment is separated by colons.
Your posting said that you want to "add a path in my home directory to a piece of matlab software" - adding a path to an application is different thing. For that you will need to use the application's preference interface or configuration file, I guess.