If you've wanted to try the preview of Office for Android tablets during its brief history, you've had to request to join a Google+ group. That's not the hardest thing to do, but do you really want to participate in a special club (and in some cases, sign up for Google+) just to try some productivity apps a little early?
As of now, you don't have to. Microsoft has posted the previews of Excel, PowerPoint and Word on Google Play, so you can download them like you would any other app. The only major requirements are that your slate runs at least Android 4.4 KitKat and that you're comfortable with less-than-polished software.
You may not want to finish an important report with these releases, then, but it's now easy to experiment with the new Office suite before it's completely ready.