TortoiseSVN is a subversion client. It allows you to manage the files on your machine that are under control of subversion. It is the GUI that provides access to the subversion repository. The model is rather like a database and the code that accesses the database. The subversion server provides the database and the client is that which accesses it.

Bottom line: TortoiseSVN is a great client and you have done the right thing installing it. Now all you need to do is figure out how to use it to access the author's SVN repository.