After saving a form, go to Settings → Access where you can find Access management and toggle Allow only authenticated users to enable authentication.
Select Microsoft Account:
Once you turn it on — users will need to be authorized:
You can restrict submissions to just one per user:
If you do — you can also allow users to go back to form and edit their submission (each edit counts as a separate submission):
Finally, you can restrict access to specific users by enabling Restrict access to specific users or groups (Azure AD) and inputting a Microsoft 365 domain:
This will require you to authorize the app to access domain and retrieve information about users and groups:
On top of that, you will also be able to select specific Azure Active Directory groups or even individual users to provide access to:
Users without permissions will not be able to access the form: