Hi adirakun,
The template you have downloaded is perhaps the most complicated one to use on the website since a thesis is inherently a complicated document. If you are new to LaTeX I would recommend you start by reading the LaTeX WikiBook here:
http://en.wikibooks.org/wiki/LaTeX and then try out some of the simpler templates on the website such as this formal letter:
http://www.latextemplates.com/template/ ... mal-letter or this essay:
http://www.latextemplates.com/template/ ... oned-essay. That should give you the knowledge you need to understand the thesis template.
Regarding that specific template, you do not need to worry about the sty file. The main "ClassicThesis.tex" file essentially bundles together all the other tex files into the thesis. If you look through it you will see where each one is included via, for example, "\include{FrontBackmatter/Titlepage}". You then navigate to the FrontBackmatter directory and open the Titlepage.tex file to edit the title page. If you work your way through every \include you will see what you need to edit where. Every tex file is extensively commented by me so it shouldn't be a problem to fill them out.
Hope that helps!