How to restrict signing into Azure AD administration portal?

Step 1: Sign into http://portal.office.com/ and click on Admin.

Step 2: Navigate to Azure Active Directory.

Step 3: In the Azure Active Directory admin center, click on Azure Active Directory on the left pane.

Step 4: Scroll down and click on User settings.

Step 5: Under Administration portal, click No.

Step 6: Click Save.