Hi tasha_carolina,
Congratulations on your new Apple Watch. For help with setting up the Sleep feature, test the steps below found in the article here: Track your sleep on Apple Watch and use Sleep on iPhone
"Set up Sleep
Getting enough sleep is important to your overall health. The Health app on iPhone can help you set a sleep goal, and track your progress over time in meeting that goal.
- Open the Health app on your iPhone.
- Tap Get Started under Set Up Sleep, then tap Next.
- Follow the onscreen prompts to establish:
- Sleep Goals: Set the number of hours you'd like to spend asleep.
- Bedtime and Wake Up times: Set when you'd like to go to bed and wake up.
- Sleep Focus: To reduce distractions, iPhone can simplify your Lock Screen and turn on Sleep Focus at your scheduled bedtime. You can also give certain people or apps permission to notify you. Learn how to customize a Focus.
- Track Sleep with Apple Watch: Wear your watch to bed to track your sleep. This option is available during setup if you've paired your Apple Watch with your iPhone beforehand. If you pair your Apple Watch after setup, you can still turn on Track Sleep with Apple Watch later."
Be sure to also complete and view the details in the section "Get more accurate results with your Apple Watch" at the bottom of the article.
You can also find helpful information here: Track your sleep with Apple Watch
If the issues continue, reach out to Apple Support directly to further assist.
Contact - Official Apple Support
Contact Apple for support and service - Apple Support
Best.