This is a LaTeX documentclass for making a Master's thesis at the University of Helsinki. This is primarily for the Department of Physics because the theses look very different at different departments.
Keep the HYgradu.cls file and sinetti.pdf in your working directory when writing the .tex file.
Add HYgradu.cls and sinetti.pdf to your LaTeX distribution tree to use it from any directory. Of course, this is a package you only usually need once so it's not that important.
The simplest way is just to take the template provided with the class file and start editing that.
Please send any bug reports or suggestions to olli.wilkman@iki.fi. Contributions on Github are also welcome.