Hi, I'm Bernard, a fellow Windows user. I'm happy to help!
To set the screentime, kindly follow the steps below:
Go to this link: https://account.microsoft.com/family
Then select the family member whose screen time you want to change.
Then select the tab for the platform (Windows, Xbox, or Mobile)
Then follow the prompts to change the limit
You may also refer to the link below: https://support.microsoft.com/en-us/account-billing/set-screen-time-limits-across-devices-a593d725-fc4c-044c-284d-32eab0305ffd