Lakshmana, not sure what you're referring to?
What is the requirement? Are you trying to create new fields in Marketo or just add fields to a form?
Same question, you want to create a new field?
Do a search for "create new field in marketo" and you'll find what you need.
Admin>Field Management>New
if this is a Marketo only field, that's ok. If you need Salesforce to see it, you should create it in SFDC first.