Hi Petasek, welcome to the community.
It is not possible to bypass attendee registration for GoTo Webinar, every attendee joins using a unique join link that is emailed to them. There are integrations and an API available that can be used to connect to 3rd party platforms for registration, but as you have already registered them you could use Bulk Registration feature to upload their details.
You will want to let the attendees know that you are registering them for the session so that they do not treat the email with their unique join link as SPAM. Bulk Registration should only be used with attendees that have consented to being registered.
