Try using the program called "Calibre". There are lots of bits of information on this site about how it works etc. You can then move files onto your Kobo, manage ebooks on your computer and do a whole lot of very useful stuff. As you are probably not a techie (I presume this is so?) read the
http://calibre-ebook.com/user_manual/, the user manual, or at least the basic parts. I think you will find this is a best software for non DRM ebooks around.