Welcome to T-Mobile and our Support Community! I'm going to assume that this is the device you're using: T-Mobile 665 In case you still haven't been able to set-up your My T-Mobile account, let's try this:
To find your T-Mobile number: Go to Settings > Call Settings > My numbers > My number
To read messages: Messaging (SMS/MMS): T-Mobile 665
Please try following those steps and let me know if you're able to sign-up for your My T-Mobile account.
Yes, when I logged into the hotspot with a web browser there was a tab for sms and thats where the code was. All good. Thanks!