On the first day, take the earliest boat from Sanur Harbour. The ticket prices vary between $15-26 US, and you can buy them at the harbor or online. Arrive 30 minutes before departure and travel as light as possible, as you will need to carry all your belongings to the boat yourself.
Once you arrive on Nusa Penida, you can either rent a scooter or hire a local driver for a day tour around the island. The most convenient way to travel around Nusa Penida is with a local driver, as some of the roads can be difficult to navigate on a scooter. I advise to look for a local driver online before you arrive in Nusa Penida to save you the haste of looking for one. Start your first day with a West Nusa Penida tour, exploring Keling King Beach, Angel's Billabong, and Broken Beach.
At the end of the day, check into your accommodation and find a spot to watch the sunset, like Amok Sunset, a restaurant with amazing views!