Thank you for reaching out.
To try on MS Graph APIs - you can leverage Graph Explorer.
If you do not sign in here, there is some test data available for you to try. This is applicable for all GET endpoints.
Being said that, you can try these Graph tutorials which are step-by-step training exercises that guide you through creating a basic application that accesses data via the Microsoft Graph. You will need to create an Azure AD application though. You can create your free Azure account. Check here.
If you already have an Azure subscription and are not able to access graph, Please revert back with the exact error and how are you using so it is more clear.