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1. Login to Microsoft Azure with the tenant admin credential
2. Click on 'Azure Active Directory'->'App Registrations'
3. Create a 'New registration' & copy the application (client) id
4. Under 'Clients & certificates' create a 'new client secret' & copy the 'client secret'
5. Under 'API permissions' -> 'Add a permission' -> Select 'Microsoft Graph' -> Select 'Application permissions' -> search for & add 'ExternalItem.ReadWrite.All'
6. Grant admin consent by clicking the 'Grant admin consent for <tenant>'

For detailed documentation on application registration, refer: register an app.
For details on tenancy & creating multi-tenant apps, refer: Tenancy in Azure Active Directory.
For details on pre-authorization flow & different ways to consent, refer: Consent to an application.

Windows or Linux

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The Microsoft Search publisher run on either Windows or Linux.

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