Hello, userheidiromeo.
I have the steps to help you change your iPad's screen orientation.
Make sure to turn off the Portrait Orientation lock for your iPad. Swipe down from the top-right corner of the screen, then tap the lock icon.

Then, rotate your iPad horizontally to re-orient it.
Also, you can reach out to Apple's support if you don't have the Portrait Orientation lock. They can guide you in changing the screen orientation on your iPad device.
Ready to work on your QuickBooks Self-Employed account after changing the orientation? Feel free to check our articles if you need help with something like categorizing transactions or taking care of your estimated taxes. Browse them in the Self-Employed articles list.
This thread is still open if you have more questions with your Self-Employed account. I'm here to help you out.