Hi @Cing An Yong Greetings! Welcome to Microsoft Q&A forum. Thank you for posting this question here.
If you try to access the Azure Digital Twin explorer from the Azure portal Azure Digital Twin overview page, it should resolve the instance URL and automatically connect to your instance. Please refer the below image from where you can launch the Azure Digital Twin Explorer.
If you see a prompt asking for Azure Digital Twin instance URL when you launch the Azure Digital Twin Explorer, you need to copy the Host name from the above ADT instance overview page and provide in the pop up as follows.
Please note that the Azure Digital Twins Explorer can only access Azure Digital Twins instances with public access enabled. If you're using Private Link to restrict access to your instance through a private endpoint, you can use Azure functions to deploy the Azure Digital Twins Explorer codebase privately in the cloud. For instructions on how to do this, see Azure Digital Twins Explorer: Running in the cloud.
Hope this helps. Please let us know, through the comments below, if you still experience any issues after trying out the above steps. We would be happy to help you.
If the response helped, please do click Accept Answer and Yes for the answer provided. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.