How to create duplicate records in "MARKETO"

You should start by searching the Community for "duplicate records." We discuss this all the time and there are informative posts going back years.

Also, this thread should be in Products​ so please move it there ("Central" is for discussing general marketing ideas, not topics this specific to Marketo). But before continuing please do a thorough study of what's already out there, both in Community discussions and official Marketo blogs.