See section at the end of: https://costcertified.atlassian.net/wiki/spaces/CS/pages/1126694956/Build+a+lead+form+for+your+website#Adding-custom-fields
Manage space
Manage content
Integrations
See section at the end of: https://costcertified.atlassian.net/wiki/spaces/CS/pages/1126694956/Build+a+lead+form+for+your+website#Adding-custom-fields