@CatherineEleen :
1. Can you check that when you landed in the Migration tool Scans tab, the connection was successful? To check that, you should see a green dot and the word 'Connected' on the top right corner of the screen.
2. No, you don't need to add the containers manually via CSV. When you landed on the Scans tab it triggers auto-discovery of content in your tenant. It takes upto 15 mins for first set of containers to appear, if you have large data. Can you click on "Look for new Containers" from inside "Add containers" menu and wait for 15-20 mins.
Refer to public docs when you are running the tool https://learn.microsoft.com/en-us/stream/streamnew/step-by-step-guide
If both the above things don't work, you can reach out to us by raising a CRI. Do mention your tenant id in the CRI.
