Hi @Dinah ,
Thank you for posting in this community.
You can break permission inheritance for the specific page. Sets unique permissions for the page, removes permissions for others, and grants access only to selected colleagues.
Here are steps:
1.Click on the three dots next to the page name,click "Manage Access"
2.Click "Advanced Setting"
3.To break permissions inheritance from the parent, select Stop Inheriting Permissions.
4.Assign unique permissions (Grant selected colleagues permission and remove other user permission).
More detailed step-by-step information, you can refer to this article:https://support.microsoft.com/en-us/office/customize-permissions-for-a-sharepoint-list-or-library-02d770f3-59eb-4910-a608-5f84cc297782
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