Hi Durai,
If you have just the Azure AD then you can follow the steps in the below link,
If you have office 365 account then please follow these steps :
1. Go to sdpondemand.manageengine.com
2. In the "Login" page, click on "Sign In using Office 365" icon
3. You will be redirected to Microsoft login page
4. Use your Office 365 credentials and Login
5. After Login, you will be redirected to SDP On-Demand
6. Go to Admin ---> Users ---> Requesters page
7. Click on "Import Users" drop down
8. You will see an option "Import from Azure", now you can select users and import
Before import, please make sure the email domain is added and verified in Setup-->Organization Details-->Domain details page. If the domain is not verified then the users will get invitation emails during import to join the Organization.
Once imported, users can click on "Sign In using Office 365" and login to SDP On-Demand.
ServiceDesk Plus On-Demand app is also available in Office Store. Users can add the app and then Login to SDP On-Demand in one click from their Launcher.
Please get back to us for further clarifications.
Thanks & Regards,
Ram
ServiceDesk Plus OnDemand Support