Hi Daniyal,
Before you can create a Virtual Machine, you need to click Activate sandbox, review/accept permissions when prompted. Once the sandbox is active it will show the amount of time remaining (it is only valid for 1 hour). When you see this time remaining you can click the link to go to the Azure portal and create your VM.
Please note that once the sandbox expires the sandbox subscription and any resources you created will be automatically deleted. If this happens you can activate a new sandbox and create new resource(s) again.
Please click Accept Answer if the above was useful. If you still need assistance please add a comment below.
Thanks.
-TP