Can I add an Authorized User into my T-Mobile Acct online by myself?

Greetings to All,

Just transferred my cell #s to T-Mobile today 02/21/2024.

I have a question about how I can add an Authorized User to my T-Mobile Acct online.

I found this post, which was posted 4 years ago. I'm not sure if it still applies today.

Can anyone please show me detailed step-by-step instructions?

¡Gracias!