If it is a paper push, you need the professor to write a form written by the other school, which is basically an evaluation of your ability and then sign and mail it to the other school.
If it is an online tweet, you will be asked to fill out a form, including some information about the professor. The most important thing is that you fill in the professor's email address, and then the other party will send an email with your name to this email address. There is a link in the email. Click it to fill in the recommendation form.
If you do it yourself, you usually ask the professor to forward the email to you, and then you can do it yourself. I guess the intermediary did the same. Communication means asking professors to forward emails.