They have had the beta version 4 out for a while but to stay current.
Google Earth download link is where you will want to go in order to stay current with this.
Since most of the computers I see either have google earth on it, be sure to stay current as this will eliminate the many questions I get as to "my computer is not working", when in fact it is the program that isn't working correctly.
As with many programs, when you have it running, click on the HELP which is usually found at the top of the window. Within this HELP menu, quite often you will find "check for new versions" or "check for updates". If this isn't there, then there will usually be a link to the product home page where you can find out about any updates or newer versions.