Thank you for sharing your concern here in the Community. Allow me to share some information about changing your QuickBooks Online (QBO) account to QB Self-employed (QBSE).
If you're currently using QuickBooks Online, you can cancel your subscription from there. Then, resubscribe as soon as you sign in to your QBSE account. To guide you further, you can follow these steps:
If you want to cancel your QBO account (in case you're using it now), here are the steps to follow:
Sign in to QuickBooks Online as an admin user.
Go to the Gear icon.
Choose Account and settings.
Go to the Billing & Subscription tab.
In the QuickBooks section, tap Cancel subscription or Cancel online. If you're canceling a trial, hit Cancel trial.
Follow the onscreen steps.
Resubscribe to QuickBooks Self-Employed:
Sign in to QuickBooks Self-Employed on a web browser.
Press the profile icon and then Billing info.
Click Subscribe.
Review your billing and payment info.
Tap Subscribe.
Additionally, I've collected some articles about handling transactions and other details in QBSE: