Your account has been created, you should be able to reset your GNOME Account password via:
Once done, please login with your username and the password you just set at the following website:
You will then be able to manage your account including adding SSH keys which will then be automatically syncronized against GitLab. Please also remember your GNOME Account allows you to login against all the hosted services including Discourse, Events website, Pastebin, Nextcloud, Gitlab etc.