Search Center settings
As a SharePoint Online administrator, you can specify where searches should go by specifying the URL of your Search Center. For example, if you have created an Enterprise Search Center where users can search everything in your company, you can enter the URL of that site here.
Enter the address of your Search Center
Sign in to the Office 365 Admin Center.
Choose Admin > SharePoint. You're now in the SharePoint admin center.
On the search administration page, choose Search Center Settings.
In the Search Center URL box, type the URL of the Search Center site.
Note: It may take up to 30 minutes before changes take effect.