The registrar form whom you are moving the name will send you an email (to the email address listed in the account) within a couple days of the request. If you agree with the transfer then usually you do nothing, if you want to stop it then follow the instructions in the email. There is a cut-off date to block the transfer, something like five days.
Check your spam filter if you have not seen the email in a couple days.
If you stop a transfer then you may have your payment stuck at the registrar where you were going to send it.