There is no easy way which is not to say the process is difficult. You log out of wordpress.com. Go here > http://wordpress.org and on the top right hand corner of that page register a wordpress.org username account as all your support must come from there - not from here.
You hire a web host, your set up a wordpress.org install, equip it with a theme and plugins. Then you export your content out of your wordpress.com blog into a wordpress.org install. http://en.support.wordpress.com/export/ The text widget content is not exportable and must nbe copied and pasted. The widgets in the wordpress.org install will not include the many "in-house" wordpress.com widgets.
After you have installed and activated the JetPack plugin you return to this support forum and provide both URLs and Staff will transfer your email subscribers only (follwers who use the Reader cannot be transferred.)
You will be responsible for all upgrades, installations, backups and troubleshooting. If you install a theme or a plugin that negatively affects your blog, then you have to figure out what went wrong and fix it.