If you don't have a membership, you can use Hydrow in Just Row mode. In this mode, you'll be able to adjust resistance levels, view Hydrow 101 and introductory materials, use the onscreen rowing metrics during the workout, and connect with Bluetooth for the heart rate monitor only.
You'll need a membership to access prerecorded and live workouts, music, any stored records of progress (you also won't be able to save your current results), weekly challenges, and access to the leaderboard. One thing to keep in mind is that even Just Row mode requires internet access and a working electrical outlet.