Note: beta products usually haven't been subjected to the same reliability, availability, and security testing as other Dropbox products. You can uninstall the beta version and revert to the regular Dropbox app at any time.
Learn more about the Dropbox early access program.
This beta program is limited and may reach capacity. If it reaches capacity, wait a little and try to join again.
If you're on an Android device:
Simply visit the beta testing sign-up page.
Once you've installed the beta version, you'll receive updates regularly through the Google Play Store.
If you're on an iOS device:
First, download Apple's app called TestFlight.
After installing TestFlight, open this link from your phone or tablet and follow the on-screen instrutions.