Upgrading is a simple task. In general, you want to make sure you backup your site files and database and then upload the new release files to your site. After uploading all of the files, run the Setup script at http://yoursitename.url/Setup/Default.aspx.
You should read the upgrade documentation here: http://www.mojoportal.com/upgrading.aspx and you should also go through the release notes for each release between your version and the current version. These release notes can be found in the blog here: http://www.mojoportal.com/Blog/ViewCategory.aspx?cat=8&mid=19&pageid=2.