Ready to go?  Please read all these pinned topics before starting…

You can do a fresh install or upgrade from 4.4.5. 

If you upgrade, one of the first things you will notice is the plugin directory structure has completely changed…  within the wp plugins directory, the simple press plugin is now in a directory called simple-press (not simple-forum).  so if upgrading, you will want to complete remove the old plugin before uploading the new plugin. 

please run from svn to stay up to date. There is a whole topic on getting that set up.