If the publisher of the worflow performed the step reecardo illustrated it's likely the form is in the list, just not visible to you based on ProcessManager permissions. Maybe have that user login to the portal and update permissions of the published form?

Otherwise, adding a form manually is a relatively simple process if you've been provided, or have access to, the necessary details. You just need the name of the virtual directory (from the first page of the publishing dialog or from looking at virtual directories in IIS) and the start page if it's been changed (default is StartDialog.aspx). Once this info is known edit a standard SD form such as the General submission form to view the configured settings. Based on my example the URL would be /SD.Feeder.GeneralIncidentSubmitForm/StartDialog.aspx, enable passing the session ID named EnsembleSessionID, configure permissions to allow others to see them, etc.